Private Sub Text1_KeyPress(KeyAscii As Integer)
  If Not InStr("0123456789", Chr$(KeyAscii)) = 0 And KeyAscii <> vbKeyBack _
    Then KeyAscii = 0
End Sub

Private Sub Text1_KeyPress(KeyAscii As Integer)
  If InStr("AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzÄäÜüÖöß" & Chr$( _
    8), Chr$(KeyAscii)) = 0 Then
    KeyAscii = 0
  End If
End Sub