How Can I tell if a user Control is running at design Time

I want to Subclass a user control so that it changes the window bitmap when the mouse goes up and down (Before the window is redrawn so I can't use the mouseup and mouseDown events), but I'm very cautios about messing about with wndow Procedures at design time and then expecting it to work at run time. Is there a way of telling if the program is running at runtime or design time, ie when do I swap the windowprocs.

It's probably a lot easier than i've made out but I'm not very good at explaining things.

Thanks

I think (not positive) that UserControl.AmbientProperties.UserMode and = False for design time and true for run time.

Cool It works Thanks