first of all, do this:
//your header file (xxxxx.h)
void Notify(HWND,long int);
i tried an example just like this, it worked and compiled perfectly. i included the .h above in 3 diff .cpp file. one of them was the example .cpp i showed above. this way you're defining in the cpp not the h. in the h you are just declaring.
//your .cpp file
void Notify(HWND hwnd,LPCTSTR str)
void Notify(HWND hwnd,long int num)
if that doesn't work then im going to shoot myself and yourself because it MUST WORK! i just tried it!