Private Sub IS_TextBox_KeyPress(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.KeyPressEventArgs) Handles Me.KeyPress
 
            If Not Asc(e.KeyChar) = 8 And Then
                myText = Text_to_mySQL(Me.Text & e.KeyChar)
                e.KeyChar = Chr(0)
            Else
                e.KeyChar = e.KeyChar
                e.Handled = True
                ' Hier entsteht der Fehler!
                myText = Text_to_mySQL(Me.Text)
                ' myText = Text_to_mySQL(Me.Text & e.KeyChar) geht auch nicht!
                Exit Sub
            End If
            e.Handled = True
        End Sub