Sub vergleichen()
Dim B1 As Object, B2 As Object
Dim zeile As Long, erg As Variant, Mittlg As String
Set B1 = ActiveWorkbook.Sheets(1)
Set B2 = ActiveWorkbook.Sheets(2)
With B1
For zeile = 2 To .Cells(Rows.Count, 1).End(xlUp).Row
Set erg = B2.Columns(1).Find(what:=.Cells(zeile, 1), lookat:=xlWhole)
If erg Is Nothing Then
Mittlg = Mittlg & IIf(Mittlg = "", "", "; ") & .Cells(zeile, 1)
End If
Next zeile
End With
If Mittlg = "" Then Mittlg = "alle Ds vorhanden"
MsgBox Mittlg, vbOKOnly, "noch nicht erfasste IDs"
End Sub