Excel 2003 SP3 - Makro - fehlerhafte Zusammenführung der Daten von zwei seperaten CSV-Tabellen

Sub MergeSheets()

    ' opens two workbooks and merges data from the second to be opened into the first one  

    Application.ScreenUpdating = False

    Dim Sourcefile As String 'opens sourcefile (where date are merged in)  
    With Application.FileDialog(msoFileDialogOpen)
        .Title = "file to be merged in"  
        .Filters.Add "csv-file", "*.csv"  
        .Show
        Sourcefile = .SelectedItems(1)
    End With
    On Error Resume Next
    
    Dim Gridfile As String 'opens gridfile (where date come from)  
    With Application.FileDialog(msoFileDialogOpen)
        .Title = "file containing the grid fields"  
        .Filters.Add "csv-file", "*.csv"  
        .Show
        Gridfile = .SelectedItems(1)
    End With
    On Error Resume Next
        
    'getting the filename of the gridfile-dir-string to close it later  
    Dim x As Variant
    x = Split(Gridfile, "\")  
    Gridfile = x(UBound(x))
        
    'file with data to be copied out of being opened  
    Workbooks.Open Filename:=Gridfile
    Workbooks(Gridfile).Worksheets(1).Activate
    'range to be copied will be determined  
    Range("A1", Cells(ActiveSheet.UsedRange.Rows.count, ActiveSheet.UsedRange.Columns.count)).Select  
    Selection.Copy
    
    'file the date to be copied into being opened  
    Workbooks.Open Filename:=Sourcefile
    Workbooks(Sourcefile).Activate
    'data where merged into the sourcefile  
    Dim NewPrColumn As Integer
    NewPrColumn = ActiveSheet.UsedRange.Columns.count + 1
    Cells(1, NewPrColumn).Select
    ActiveSheet.Paste
    
    'now the big one: sort-algorithm  
    
    Dim i As Integer
    Dim j As Integer
    Dim sPrID As Integer
    Dim gPrID As Integer
     
    For i = 2 To ActiveSheet.UsedRange.Rows.count
        sPrID = Cells(i, 1).Value
        gPrID = Cells(i, NewPrColumn).Value
        If gPrID > sPrID Then
            If Not sPrID = 0 Then
                Range(Cells(i, NewPrColumn), Cells(i, ActiveSheet.UsedRange.Columns.count)).Insert
            End If
        End If
        If gPrID < sPrID Then
            If Not gPrID = 0 Then
                Range(Cells(i, 1), Cells(i, NewPrColumn - 1)).Insert
            End If
        End If
    Next i
    
    ' draw lines  
    For i = 2 To ActiveSheet.UsedRange.Rows.count
        If Not Cells(i, 1).Value = Cells(i + 1, 1).Value Then
            Rows(i).Borders(xlEdgeBottom).LineStyle = xlContinuous
        End If
    Next i
    
    
    'gridfile-workbook is being closed - all relevant data are in the sourcefile-workbook now  
    Workbooks(Gridfile).Close savechanges:=False
    Application.ScreenUpdating = False
    
    ' Überschrift Fett machen, sonstige Grafische Einstellungen  
    Rows(1).Font.Bold = True
    Rows(1).VerticalAlignment = xlTop
    Rows(1).Borders(xlEdgeBottom).LineStyle = xlContinuous
    Columns(NewPrColumn).Borders(xlEdgeLeft).LineStyle = xlContinuous
    Columns(NewPrColumn).Borders(xlEdgeLeft).Weight = xlThick
    Dim dummy As String
    dummy = Cells(1, 1).Value
    Cells(1, 1).Value = dummy & vbLf
    Range(Cells(1, 1), Cells(ActiveSheet.UsedRange.Rows.count, ActiveSheet.UsedRange.Columns.count)).Select
    With Selection
        .Borders(xlEdgeTop).LineStyle = xlContinuous
        .Borders(xlEdgeTop).Weight = xlThick
        .Borders(xlEdgeLeft).LineStyle = xlContinuous
        .Borders(xlEdgeLeft).Weight = xlThick
        .Borders(xlEdgeRight).LineStyle = xlContinuous
        .Borders(xlEdgeRight).Weight = xlThick
    End With
    
    ' Kopf und Fußzeilen festlegen  
    With ActiveSheet.PageSetup
        .CenterFooter = "page &P of &N"  
        .CenterHeader = "" & Überschrift  
        .RightHeader = "&D"  
        .PrintTitleRows = "$1:$1"  
        .Orientation = xlLandscape
        .CenterHorizontally = True
        .Zoom = False
        .LeftMargin = Application.InchesToPoints(0.196850393700787)
        .RightMargin = Application.InchesToPoints(0.196850393700787)
        .FitToPagesWide = 1
        .FitToPagesTall = 10000
    End With
    
End Sub