Deriving classes in AFCL in NewEra

I'm currently developing a forms-based application in NewEra 3.11 using the Application Framework Class Library (AFCL) and I'm really struggling in my attempts to expand the base classes. My next task (of many) is to try to enhance the Browser Window to include a horizontal slide bar, a cancel button and a more readable header. Is there anyone out there who's done this kind of thing? My initial attempts seem very long-winded and I'm having a lot of trouble getting AFCL to use my derived class rather than the base class. Many thanks, Andy Kent Bristol, England