Private Function Tastencode(intKeyAscii As Integer) As Integer
  If Not KeyAscii >= 48 And KeyAscii <= 57  And _
     Not intKeyAscii = 8 Then
    Tastencode = 0
    Exit Function
  End If
  Tastencode = intKeyAscii
End Function
 
Private Sub [Textfeld]_KeyPress(KeyAscii As Integer)
  KeyAscii = Tastencode(KeyAscii)
End Sub