The problem is that every object needs some code in the Click Event, and if I do it with the original class for this object, there will be not code.

If you are using VFP 8.0, you can do this without a subclass by using BINDEVENT() to bind the click event of the control to your custom form method.

I tried to put the class I'd created in the form, but it tells me "Class XXXXXXX have not been defined".

The AddObject() method requires that the classlib be loaded using

SET CLASSLIB TO << My Vcx >> ADDITIVE 

or

SET PROCEDURE TO << My Prg >> ADDITIVE