I've managed to use a combination of these ideas so that a When method sets the internal llAccessible and my code checks that before running anything.

By the way a custom control does not have the SetAll method.

This has thrown up another problem :)

When the user click on the right commandbutton the Control's GotFocus is run (calling the When) the CommandButtons GotFocus is then called. However when a MessageBox is activated this seems to prevent the CommandButtons Click from being called.
Any ideas?