Private Sub sevWerbe_Validate(Cancel As Boolean)
    Cancel = False
 
    If IsNull(sevWerbe) Or sevWerbe = "" Then
       Aktion = MsgBox("Eingabe zwingend, erfassen?", vbOKCancel + vbCritical, _
         "Eingabe")
       If Aktion = vbCancel Then
          sevWerbe.CausesValidation = False
          Exit Sub
       Else
          Cancel = True
          Exit Sub
       End If
     End If