static CWnd* GetCapture();
Retrieves the CWnd that has the mouse capture. Only one window has the mouse capture at any given time. This window receives mouse input whether or not the cursor is within its borders.
The CWnd receives the mouse capture when the SetCapture member function is called.
Identifies the window that has the mouse capture. It is NULL if no window has the mouse capture.
The return value may be temporary, and should not be stored for later use.
CWnd::SetCapture, ::GetCapture