This function locks or unlocks the visible regions of all the windows on the screen, preventing any of the visible regions from changing.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND    hwndDesktop;  /*  Desktop-window handle or HWND_DESKTOP. */
BOOL    fLock;        /*  Indicates whether the visible regions are being locked or unlocked. */
BOOL    rc;           /*  Success indicator. */

rc = WinLockVisRegions(hwndDesktop, fLock);