How do you Know if the user want's a return value?

Does anyone know if there's a way for findong out from inside a public function in a usercontrol wheather the user wants a return value or not, ie wheather the user has gone

lngMyVariable=MyFunction(MyParam1,MyParam2)

or just

MyFunction MyParam1,MyParam2.

This would be seriously helpful.

You should always return some meaningful value from all functions. That way the user can decide how he calls your function and it won't matter to you. The return value could be something as simple as a True/False boolean indication sucessful completion.

Sorry I didn't make myself clear, It's for a control to make subclassing a bit safer. I need to lnow if the user has got a return value when they call the default window function, if they don't I need to return this value from my substitute window process by default, If they don't they may well have other plans for my return value so I don't want to change it.