Private Sub TextBox1_KeyPress(ByVal Sender As Object, ByVal e As _
  KeyPressEventArgs) Handles TextBox1.KeyPress
  Dim result As MsgBoxResult
 
  result = MsgBox("Es wurde " & e.KeyChar & " gedrückt." & vbNewLine & "Eingabe" & _
    "zulassen?", MsgBoxStyle.Question Or MsgBoxStyle.YesNo, "Eingabe")
 
  'Wenn True: Auswahl zulassen
  e.Handled = result = MsgBoxResult.Yes
 
End Sub