Option Explicit

Dim Zahlen As Boolean

Private Sub Text1_KeyPress(KeyAscii As Integer)
  If Zahlen = True Then
    Select Case KeyAscii
      Case Asc("0") To Asc("9"), 8, 13 'inkl. BackSpace & Return
    Case Else
      KeyAscii = 0
    End Select
  End If
End Sub

Private Sub Command1_Click(Index As Integer)
  Select Case Index
    Case 1
      Zahlen = True
      Label1.ForeColor = &HC0&
      Label1.Caption = "Nur Eingabe von Zahlen erlaubt!"
      Text1.SetFocus
    Case 2
      Zahlen = False
      Label1.ForeColor = &H0&
      Label1.Caption = "Jetzt sind alle Zeichen erlaubt!"
      Text1.SetFocus
    Case Else
      Unload Me
      End
  End Select
End Sub