This function sets rectangle coordinates.

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

HAB       hab;       /*  Anchor-block handle. */
PRECTL    prclrect;  /*  Rectangle to be updated. */
LONG      lLeft;     /*  Left edge of rectangle. */
LONG      lBottom;   /*  Bottom edge of rectangle. */
LONG      lRight;    /*  Right edge of rectangle. */
LONG      lTop;      /*  Top edge of rectangle. */
BOOL      rc;        /*  Success indicator. */

rc = WinSetRect(hab, prclrect, lLeft, lBottom,
       lRight, lTop);