This example uses the WinSetSysValue call change the sizing border dimensions.

#define INCL_WINSYS
#include <OS2.H>
LONG vlXBorder, vlYBorder;

vlXBorder = WinSetSysValue(HWND_DESKTOP,
                           SV_CXSIZEBORDER,
                           20L);
vlYBorder = WinSetSysValue(HWND_DESKTOP,
                           SV_CYSIZEBORDER,
                           20L);