This function captures all pointing device messages.

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

HWND    hwndDesktop;  /*  Desktop-window handle, or HWND_DESKTOP. */
HWND    hwnd;         /*  Handle of the window that is to receive all pointing device messages. */
BOOL    rc;           /*  Success indicator. */

rc = WinSetCapture(hwndDesktop, hwnd);