With the help of Sergey (-SA), in another question with a complete different topic, I found the Solution by myself.
It must be done with Reflection and calling the Event-method in the Parent-Control.
Here is a code-snippet which shows how it could be done :
Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
Dim onclick1 As System.Reflection.MethodInfo = Button1.[GetType]().GetMethod("OnClick", System.Reflection.BindingFlags.NonPublic Or System.Reflection.BindingFlags.Instance)
onclick1.Invoke(Button1, New Object() {New EventArgs()})
End Sub
In this case the Button2 uses the method inside the Button1.
The Event is raised by Button1 and not by Button2.
At this place again my thank to Sergey for his assistance and inspiration ... :)