DosError

#define INCL_DOSMISC

USHORT  rc = DosError(Flag);

USHORT           Flags;          /* Action flags */

USHORT           rc;            /* return code */

Example 

This example disables hard error popups and exception popups, then 
re-enables them. 

#define INCL_DOSQUEUES

#define ENABLE_EXCEPTION 0
#define DISABLE_EXCEPTION 2
#define ENABLE_HARDERROR 1
#define DISABLE_HARDERROR 0
#define DISABLE_ERRORPOPUPS DISABLE_EXCEPTION | DISABLE_HARDERROR
#define ENABLE_ERRORPOPUPS ENABLE_EXCEPTION | ENABLE_HARDERROR

USHORT rc;

   rc = DosError(DISABLE_ERRORPOPUPS); /* Action flag */
   rc = DosError(ENABLE_ERRORPOPUPS);  /* Action flag */