I am trying to handle wm_mousewheel for my application.

Code:

BEGIN_MSG_MAP(DxWindow)     
  MESSAGE_HANDLER(WM_MOUSEWHEEL, KeyHandler)
END_MSG_MAP()
.
.
.

LRESULT DxWindow::KeyHandler( UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL &bHandled )
 {
     if(uMsg==wm_mousewheel)
     {
       //Perform task.
     }
     return 0;
 }

But this code doesn't work.KeyHandler doesn't receive wm_mousewheel message. I am testing this application on vista. If my approach is wrong how to handle wm_mousewheel properly? Do vista is responsible for failure in handling wm_mousewheel message?