[Win32API] RegisterWindowMessage

// 정의
const UINT WM_USER_MESSAGE = ::RegisterWindowMessage( _T( "WM_USER_MESSAGE" )  );

// 보내기
::PostMessage( HWND_BROADCAST, WM_USER_MESSAGE, 0, 0 );
::SendMessage( HWND_BROADCAST, WM_USER_MESSAGE, 0, 0 );

// 받기
BEGIN_MESSAGE_MAP( .. , .. )
ON_REGISTERED_MESSAGE( WM_USER_MESSAGE, OnFunction )
END_MESSAGE_MAP()

LRESULT ...::OnFunction( WPARAM wParam, LPARAM lParam )
{
    return S_OK;
}