REALLY GRATEFUL if someone can help.

I've been debugging this program for very long and i still cant find the problem. If u keep scrolling the child window down, it wont end(i want it to stop scrolling at 'p'). It works fine if u keep scrolling up. In particular, you might want to check the scrolling implements which is found in scroll.cpp.

The file is zipped and attached.
Compiler:VC++ 6.0