This function sets the window enabled state.

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

HWND    hwnd;         /*  Window handle. */
BOOL    fNewEnabled;  /*  New enabled state. */
BOOL    rc;           /*  Window enabled indicator. */

rc = WinEnableWindow(hwnd, fNewEnabled);