This function expands a rectangle.

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

HAB       hab;   /*  Anchor-block handle. */
PRECTL    prcl;  /*  Rectangle to be expanded. */
LONG      cx;    /*  Horizontal expansion. */
LONG      cy;    /*  Vertical expansion. */
BOOL      rc;    /*  Success indicator. */

rc = WinInflateRect(hab, prcl, cx, cy);