Displays a floating pop-up menu at the specified location and tracks the selection of items on the pop-up menu. A floating pop-up menu can appear anywhere on the screen.
call this member for internal menu, which are not created from resource.
BOOL TrackPopupMenu( UINT nFlags, int x, int y, HWND hwnd, int * pnCmdSelected = NULL )
returns the return value of the handler function, if handled else false