Sub Aktualisieren()
Dim c As Range
Dim c2 As Range
For Each c In Workbooks("Liste1.xls").Worksheets("Tabelle2").Range("B10", "B2100")
For Each c2 In Workbooks("Liste2.xls").Worksheets("Tabelle1").Range("M10", "M2100")
If c.Value = c2.Value Then
c2.Offset(0, 5).Value = c.Offset(0, 11).Value
End If
Next
Next
End Sub