This function changes the owner window of a specified window.

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

HWND    hwnd;          /*  Window handle whose owner window is to be changed. */
HWND    hwndNewOwner;  /*  Handle of the new owner. */
BOOL    rc;            /*  Success indicator. */

rc = WinSetOwner(hwnd, hwndNewOwner);