Sub Buchung(ByVal Betrag As Decimal)
        Dim Abbrechen As Boolean = False
        If Betrag < m_Dispo Then
            RaiseEvent DispoGrenze(Me, Abbrechen)
            If m_Kontostand < m_Dispo Then
                RaiseEvent DispoGrenze(Me, Abbrechen)
            End If
        Else
            m_Kontostand = m_Kontostand + (Betrag)
        End If
    End Sub
    Sub Ausgabe()                            'Ausgabe der Konten
        WriteLine("Kontonr: {0,-10} Kontostand: {1,4}     Disporahmen: {2,8}", _
          m_Kontonr, m_Kontostand, m_Dispo)
    End Sub
End Class
Public Class Test
    Private Shared WithEvents Buchung As Konto
    Shared Sub Main()
        Dim k As New Konto("123", -5000, -3000)
        k.Ausgabe()
        k.Buchung(-10000)
        k.Ausgabe()
        k.Buchung(-2000)
        k.Ausgabe()
        ReadLine()
    End Sub
    Private Shared Sub Buchung_DispoGrenze(ByVal Sender As Object, ByRef cancel _
      As Object) Handles Buchung.DispoGrenze
        MessageBox.Show("Test", "Text", MessageBoxButtons.OK, _
        MessageBoxIcon.Error)
    End Sub
End Class