Private Sub Text1_KeyPress(KeyAscii As Integer)
  Select Case KeyAscii
    Case 48 To 57, 8, 44
    Case 46
      KeyAscii = 44
   Case Else
      KeyAscii = 0
  End Select
End Sub

If KeyAscii <> vbKey1 And KeyAscii <> vbKey2 And KeyAscii <> vbKey3 And _
  KeyAscii <> vbKey4 And KeyAscii <> vbKey5 And KeyAscii <> vbKey6 And _
  KeyAscii <> vbKey7 And KeyAscii <> vbKey8 And KeyAscii <> vbKey9 And _
  KeyAscii <> vbKey0 And KeyAscii <> vbKeyBack And KeyAscii <> vbKeyDecimal Then
 
  MsgBox "Ungtültiges Zeichen"
  KeyAscii = 0
End If

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