Is there a way to restrict the format of a property defined by the user??
or a way to insert code in the Class that runs in design time??

I've tryed to do it by inserting code in the assign method but it only runs in execution time.

In few words, I want to restrict the possible values of a property added by myself to it only accept some values (like fonts, colors, pictures, or given values), I investigated a little in VB and it has the PropertySet, PropertyLet and PropertyGet events, but I can't find an equivalent in VFP.