This example disables output to a window and its children during a move operation (WM_MOVE) and then re-enables output once the move is finished.

#define INCL_WINWINDOWMGR       /* Window Manager Functions     */
#include <os2.h>

HWND  hwndLock;         /* handle of window to be (un)locked    */
BOOL  fSuccess;         /* success indicator                    */

case WM_MOVE:
     /* lock output */
     fSuccess = WinLockWindowUpdate(HWND_DESKTOP, hwndLock);

     /*
      .
      . execute window move
      .
      */

     /* unlock output */
     fSuccess = WinLockWindowUpdate(HWND_DESKTOP, NULLHANDLE);