CWnd* SetFocus();
Claims the input focus. The input focus directs all subsequent keyboard input to CWnd. The window, if any, that previously had the input focus loses it.
The SetFocus member function sends a WM_KILLFOCUS message to the CWnd that loses the input focus and a WM_SETFOCUS message to the CWnd that receives the input focus. It also activates either the CWnd or its parent.
If the current CWnd is active but doesn't have the focus (that is, no window has the focus), any key pressed will produce the messages WM_SYSCHAR, WM_SYSKEYDOWN, or WM_SYSKEYUP.
A pointer to the window object that previously had the input focus. It is NULL if there is no such window. The returned pointer may be temporary and should not be stored.
::SetFocus, CWnd::GetFocus