diff --git a/ENI2/ENI2.csproj b/ENI2/ENI2.csproj
index 1af7785f..686ed3ec 100644
--- a/ENI2/ENI2.csproj
+++ b/ENI2/ENI2.csproj
@@ -239,6 +239,7 @@
     </Compile>
     <Compile Include="Excel\DakosyUtil.cs" />
     <Compile Include="Excel\ExcelBase.cs" />
+    <Compile Include="Excel\ExcelComparer.cs" />
     <Compile Include="Excel\ExcelManager.cs" />
     <Compile Include="Excel\ExcelReader.cs" />
     <Compile Include="Excel\ExcelUtil.cs" />
diff --git a/ENI2/EditControls/CompareExcelDialog.xaml b/ENI2/EditControls/CompareExcelDialog.xaml
index ba0eb3dc..cf243be2 100644
--- a/ENI2/EditControls/CompareExcelDialog.xaml
+++ b/ENI2/EditControls/CompareExcelDialog.xaml
@@ -28,7 +28,7 @@
             </AccessText>
         </Label>
         <Image x:Name="imageSource" Grid.Row="1" Grid.Column="1" Margin="4" Source="../Resources/import2.png" AllowDrop="True" Drop="imageSource_Drop" DragEnter="imageSource_DragEnter"/>
-        <TextBox TextWrapping="Wrap" x:Name="textBoxSource" Grid.Row="1" Grid.Column="2" IsReadOnly="True" Margin="2" Drop="imageSource_Drop" AllowDrop="True" DragEnter="imageSource_DragEnter"/>
+        <TextBox TextWrapping="Wrap" x:Name="textBoxSource" Grid.Row="1" Grid.Column="2" IsReadOnly="True" Margin="2" Drop="imageSource_Drop" AllowDrop="True" DragEnter="imageSource_DragEnter" PreviewDragOver="textBoxSource_PreviewDragOver"/>
 
         <Label VerticalAlignment="Center" Grid.Row="2" Grid.Column="0">
             <AccessText TextWrapping="Wrap">
@@ -36,7 +36,7 @@
             </AccessText>
         </Label>
         <Image x:Name="imageTarget" Grid.Row="2" Grid.Column="1" Margin="4"  Source="../Resources/import1.png" AllowDrop="True" Drop="imageTarget_Drop" DragEnter="imageSource_DragEnter"/>
-        <TextBox TextWrapping="Wrap" x:Name="textBoxTarget" Grid.Row="2" Grid.Column="2" IsReadOnly="True" Margin="2" AllowDrop="True" Drop="imageTarget_Drop" DragEnter="imageSource_DragEnter"/>
+        <TextBox TextWrapping="Wrap" x:Name="textBoxTarget" Grid.Row="2" Grid.Column="2" IsReadOnly="True" Margin="2" AllowDrop="True" Drop="imageTarget_Drop" DragEnter="imageSource_DragEnter" PreviewDragOver="textBoxSource_PreviewDragOver"/>
 
         <Button x:Name="buttonCompare" Margin="2" Grid.Row="3" Grid.Column="1" Content="Compare" IsEnabled="False" Click="buttonCompare_Click"/>
     </Grid>
diff --git a/ENI2/EditControls/CompareExcelDialog.xaml.cs b/ENI2/EditControls/CompareExcelDialog.xaml.cs
index d36df072..f7cbc548 100644
--- a/ENI2/EditControls/CompareExcelDialog.xaml.cs
+++ b/ENI2/EditControls/CompareExcelDialog.xaml.cs
@@ -1,7 +1,12 @@
-using System;
+// Copyright (c) 2017- schick Informatik
+// Description: Dialogbox zum Vergleichen zweier Excel via Named cells
+//
+
+using bsmd.database;
+using System;
+using System.Diagnostics;
 using System.IO;
 using System.Windows;
-using System.Windows.Media.Imaging;
 
 namespace ENI2.EditControls
 {
@@ -10,14 +15,19 @@ namespace ENI2.EditControls
     /// </summary>
     public partial class CompareExcelDialog : Controls.StatusWindowBase
     {
+
+        #region Fields
         private string _sourcePath = null;
         private string _targetPath = null;
+        #endregion
 
         public CompareExcelDialog()
         {
             InitializeComponent();
         }
 
+        #region Drag&Drop event handler
+
         private void imageSource_Drop(object sender, DragEventArgs e)
         {
             string[] files = (string[]) e.Data.GetData(DataFormats.FileDrop);
@@ -84,14 +94,50 @@ namespace ENI2.EditControls
             }
         }
 
+        private void textBoxSource_PreviewDragOver(object sender, DragEventArgs e)
+        {
+            e.Handled = true;
+        }
+
+        #endregion
+
+        #region private methods
+
         private void EnableCompareButton()
         {
             this.buttonCompare.IsEnabled = (_targetPath != null) && (_sourcePath != null);
         }
 
+        #endregion
+
+        #region Comparison button handler logic
+
         private void buttonCompare_Click(object sender, RoutedEventArgs e)
         {
+            Util.UIHelper.SetBusyState();
+            string resultPath = Excel.ExcelComparer.Compare(_sourcePath, _targetPath, out string errorMessage);
+            if(!errorMessage.IsNullOrEmpty()) {
+                MessageBox.Show(errorMessage, "Comparison error", MessageBoxButton.OK, MessageBoxImage.Warning);
+            }
+            if(File.Exists(resultPath))
+            {
+                if(new FileInfo(resultPath).Length > 0)
+                {
+                    Process.Start(resultPath);
+                }
+            }
 
+            // reset input values
+            this.textBoxSource.Text = null;
+            this.textBoxTarget.Text = null;
+            this._sourcePath = null;
+            this._targetPath = null;
+            EnableCompareButton();
+
+            this.Close();
         }
+
+        #endregion
+
     }
 }
diff --git a/ENI2/Excel/ExcelBase.cs b/ENI2/Excel/ExcelBase.cs
index 34a2df7f..753ee783 100644
--- a/ENI2/Excel/ExcelBase.cs
+++ b/ENI2/Excel/ExcelBase.cs
@@ -29,7 +29,7 @@ namespace ENI2.Excel
 
         #region Construction
 
-        public ExcelBase(string filePath)
+        public ExcelBase()
         {
 
             _log = LogManager.GetLogger(this.GetType().Name);
@@ -45,6 +45,8 @@ namespace ENI2.Excel
 
         internal CountryMode Mode { get { return _countryMode; } }
 
+        internal Dictionary<string, Name> NameDict { get { return _nameDict; } }
+
         #endregion
 
         #region protected methods
@@ -136,6 +138,26 @@ namespace ENI2.Excel
             return result;
         }
 
+        internal void Colorize(string lookup, int color)
+        {
+            if(_nameDict.ContainsKey(lookup))
+            {
+                var range = _nameDict[lookup].RefersToRange;
+                range.Interior.Color = color;
+            }            
+        }
+
+        #endregion
+
+        #region public methods
+
+        public void Save(string path)
+        {
+            this._workBook.SaveAs(path, XlFileFormat.xlOpenXMLWorkbook, Type.Missing, Type.Missing, Type.Missing, Type.Missing, XlSaveAsAccessMode.xlNoChange,
+                Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
+            this._workBook.Saved = true;
+        }
+
         #endregion
 
         #region Dispose
diff --git a/ENI2/Excel/ExcelComparer.cs b/ENI2/Excel/ExcelComparer.cs
new file mode 100644
index 00000000..93f30c47
--- /dev/null
+++ b/ENI2/Excel/ExcelComparer.cs
@@ -0,0 +1,75 @@
+// Copyright (c) 2022- schick Informatik
+// Description: Compares excel files and highlights changes
+//
+
+using System;
+using System.IO;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Drawing;
+
+namespace ENI2.Excel
+{
+    public static class ExcelComparer
+    {
+        private static int diffColor = ColorTranslator.ToOle(Color.FromArgb(150, 150, 255)); // blue
+
+        public static string Compare(string sourcePath, string targetPath, out string errorMessage)
+        {
+            string fileName = Path.GetTempPath() + Guid.NewGuid().ToString() + ".xlsx";
+            errorMessage = "";
+            int counter = 0;
+
+            try
+            {
+                File.Copy(targetPath, fileName);
+                ExcelReader source = new ExcelReader(sourcePath);
+                ExcelReader comparison = new ExcelReader(fileName, false);
+
+                // loop through named cells
+                foreach (string name in comparison.NameDict.Keys)
+                {
+                    if (!source.NameDict.ContainsKey(name)) continue;
+                    string sourceText = source.ReadText(name);
+                    string targetText = comparison.ReadText(name);
+                    if (sourceText == null)
+                    {
+                        if (targetText != null)
+                        {
+                            comparison.Colorize(name, diffColor);
+                            counter++;
+                        }
+                    }
+                    if (targetText == null)
+                    {
+                        if (sourceText != null)
+                        {
+                            comparison.Colorize(name, diffColor);
+                            counter++;
+                        }
+                    }
+                    if ((sourceText != null) && (targetText != null))
+                    {
+                        if (!sourceText.Equals(targetText))
+                        {
+                            // turn cell blue
+                            comparison.Colorize(name, diffColor);
+                            counter++;
+                        }
+                    }
+                }
+                comparison.Save(fileName);
+                errorMessage = string.Format("{0} differences found", counter);
+            }
+            catch (Exception ex)
+            {
+                errorMessage = ex.Message;
+            }
+
+            return fileName;
+        }
+
+    }
+}
diff --git a/ENI2/Excel/ExcelManager.cs b/ENI2/Excel/ExcelManager.cs
index 14ae76b3..ee169071 100644
--- a/ENI2/Excel/ExcelManager.cs
+++ b/ENI2/Excel/ExcelManager.cs
@@ -83,7 +83,7 @@ namespace ENI2.Excel
             using (ExcelWriter ew = new ExcelWriter(fileName, isRefSheet))
             {
                 ew.WriteData(messages, core, out resultMessage, isRefSheet);
-                ew.Save();
+                ew.Save(fileName);
             }
         }
     }
diff --git a/ENI2/Excel/ExcelReader.cs b/ENI2/Excel/ExcelReader.cs
index c5fe8066..2c1af6ce 100644
--- a/ENI2/Excel/ExcelReader.cs
+++ b/ENI2/Excel/ExcelReader.cs
@@ -23,7 +23,7 @@ using System.Text.RegularExpressions;
 namespace ENI2.Excel
 {
     internal class ExcelReader : ExcelBase
-    {        
+    {
 
         internal enum ReadState { NONE, OK, WARN, FAIL };
 
@@ -33,9 +33,9 @@ namespace ENI2.Excel
 
         internal Dictionary<string, string> ImportValues { get; } = new Dictionary<string, string>();
 
-        public ExcelReader(string filePath) : base(filePath)
+        public ExcelReader(string filePath, bool openReadonly = true)
         {
-            this._workBook = _excelWorkbooks.Open(filePath, 0, true, 5, "", "", false, XlPlatform.xlWindows, "", false, false, 0, false, false, false);
+            this._workBook = _excelWorkbooks.Open(filePath, 0, openReadonly, 5, "", "", false, XlPlatform.xlWindows, "", false, false, 0, false, false, false);
             this.InitNameFields();
 
             // Determine if this is a Dakosy or BSMD Sheet
@@ -100,7 +100,7 @@ namespace ENI2.Excel
             string val = this.ReadText(lookup);
             if (!val.IsNullOrEmpty())
             {
-                val = val.ToUpper();                
+                val = val.ToUpper();
                 string portName = LocodeDB.PortNameFromLocode(val);
                 if (!justPorts) portName = LocodeDB.NameFromLocode(val);
                 if (portName.IsNullOrEmpty())
diff --git a/ENI2/Excel/ExcelUtil.cs b/ENI2/Excel/ExcelUtil.cs
index 62d4d3dd..e6e53e21 100644
--- a/ENI2/Excel/ExcelUtil.cs
+++ b/ENI2/Excel/ExcelUtil.cs
@@ -21,6 +21,8 @@ namespace ENI2.Excel
     {
         private static readonly ILog _log = LogManager.GetLogger(typeof(ExcelUtil));
 
+        #region Process Sheet (normal BSMD sheet import)
+
         internal static bool ProcessSheet(ExcelReader reader, out string readMessage, MessageCore messageCore, List<Message.NotificationClass> notificationClasses)
         {
             bool result = true;
@@ -134,7 +136,9 @@ namespace ENI2.Excel
             }
 
             return result;
-        }        
+        }
+
+        #endregion
 
         #region ATA
 
@@ -2343,7 +2347,7 @@ namespace ENI2.Excel
                     if (sheetValue != null)
                     {
                         property.SetValue(dbEntity, sheetValue);                        
-                    }                    
+                    }
                 }
                 else if (property.PropertyType == typeof(double?))
                 {
@@ -2351,7 +2355,7 @@ namespace ENI2.Excel
                     if (sheetValue != null)
                     {
                         property.SetValue(dbEntity, sheetValue);                        
-                    }                    
+                    }
                 }
                 else if (property.PropertyType == typeof(string))
                 {
@@ -2359,7 +2363,7 @@ namespace ENI2.Excel
                     if (sheetValue != null)
                     {
                         property.SetValue(dbEntity, sheetValue);                                               
-                    }                    
+                    }
                 }
                 else if (property.PropertyType == typeof(int?))
                 {
@@ -2367,7 +2371,7 @@ namespace ENI2.Excel
                     if (sheetValue.HasValue)
                     {
                         property.SetValue(dbEntity, (int)sheetValue.Value);                     
-                    }                    
+                    }
                 }
                 else if (property.PropertyType == typeof(byte?))
                 {
@@ -2375,7 +2379,7 @@ namespace ENI2.Excel
                     if (sheetValue.HasValue)
                     {
                         property.SetValue(dbEntity, (byte)sheetValue.Value);                     
-                    }                    
+                    }
                 }
                 else if (property.PropertyType == typeof(Boolean?))
                 {
@@ -2383,7 +2387,7 @@ namespace ENI2.Excel
                     string boolStringValue = reader.ReadText(lookupNameAttribute.LookupName);
                     if (sheetValue.HasValue) { 
                         property.SetValue(dbEntity, sheetValue);                     
-                    }                    
+                    }
                 }
                 else
                 {
diff --git a/ENI2/Excel/ExcelWriter.cs b/ENI2/Excel/ExcelWriter.cs
index 9a0c9098..6f06015e 100644
--- a/ENI2/Excel/ExcelWriter.cs
+++ b/ENI2/Excel/ExcelWriter.cs
@@ -18,15 +18,11 @@ namespace ENI2.Excel
     internal class ExcelWriter : ExcelBase
     {
 
-        #region Fields
-
-        private readonly string _saveFilePath;
-
-        #endregion
+       
 
         #region Construction
 
-        public ExcelWriter(string filePath, bool isRefSheet) : base(filePath)
+        public ExcelWriter(string filePath, bool isRefSheet)
         {
             string filename = @"Excel\EU-NoAD-Data-Collecting-Tool-5_0.xlsx";
             if (isRefSheet) filename = @"Excel\Reference_Sheet_DE.xlsx";
@@ -35,7 +31,7 @@ namespace ENI2.Excel
             this._workBook = _excelWorkbooks.Open(refFilePath, 0, true, 5, "", "", false, XlPlatform.xlWindows, "", false, false, 0, false, false, false);
 
             this.InitNameFields();
-            _saveFilePath = filePath;
+            
         }
 
         #endregion
@@ -196,13 +192,6 @@ namespace ENI2.Excel
 
             WriteCore(core, isRefSheet);
 
-        }        
-
-        public void Save()
-        {
-            this._workBook.SaveAs(_saveFilePath, XlFileFormat.xlOpenXMLWorkbook, Type.Missing, Type.Missing, Type.Missing, Type.Missing, XlSaveAsAccessMode.xlNoChange,
-                Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
-            this._workBook.Saved = true;            
         }
 
         #endregion