Provides entry into a section of code in which asynchronous exceptions are held.

#define INCL_DOSEXCEPTIONS
#include <os2.h>

PULONG    pulNesting;  /*  A pointer to a value that is equal to the number of DosEnterMustComplete requests minus the number of DosExitMustComplete requests for the current thread. */
APIRET    ulrc;        /*  Return Code. */

ulrc = DosEnterMustComplete(pulNesting);