The WM_HELP message indicates that the user pressed the F1 key. If a menu is active when F1 is pressed, WM_HELP is sent to the window associated with the menu; otherwise, WM_HELP is sent to the window that has the keyboard focus. If no Window has the keyboard focus, WM_HELP is sent to the currently active window.
WM_HELP lphi = (LPHELPINFO) lParam;
Returns TRUE.
The DefWindowProc function passes WM_HELP to the parent window of a child window or to the owner of a top-level window.