DosTimerAsync

#define INCL_DOSDATETIME

USHORT  rc = DosTimerAsync(TimeInterval, SemHandle, Handle);

ULONG            TimeInterval;  /* Interval size (in milliseconds) */
HSEM             SemHandle;     /* System semaphore handle */
PHTIMER          Handle;        /* Timer handle (returned) */

USHORT           rc;            /* return code */

Example 

The following example sets an asynchronous one-shot timer for one second. 
It then sets an asynchronous recurring timer with a one-second interval, 
reporting each time an interval elapses.  Finally, it stops the recurring 
timer. 

#define INCL_DOSDATETIME
#define INCL_DOSSEMAPHORES

#include <os2.h>

#define SEM_NAME        "\\SEM\\timer.sem"  /* Semaphore name */
#define TIME_INTERVAL   1000L               /* Timer interval
                                                   (in milliseconds) */

main()
{
  HSEM      SemHandle;
  HTIMER    TimerHandle;
  USHORT    i;
  USHORT    rc;

  /* Create system semaphore to be used by timers */
  DosCreateSem(CSEM_PUBLIC,        /* Ownership - nonexclusive */
               &SemHandle,         /* Semaphore handle (returned) */
               SEM_NAME);          /* Semaphore name */

  /* Set the semaphore, then start a one-shot timer */
  if(!DosSemSet(SemHandle))        /* Semaphore handle */
    printf("Semaphore set.\n");
  if(!(rc=DosTimerAsync(TIME_INTERVAL,    /* Timer interval */
                        SemHandle,        /* Semaphore handle */
                        &TimerHandle)))   /* Timer handle (returned) */
    printf("One shot timer for %f seconds started.\n", TIME_INTERVAL/1000.0);

  /* Report when timer expires (other work may be done here) */
  if(!DosSemWait(SemHandle,               /* Semaphore handle */
                 SEM_INDEFINITE_WAIT))    /* Timeout period -
                                                    indefinite */
    printf("Time interval has elapsed.\n");

  /* Start a recurring timer */
  if(!(rc=DosTimerStart(TIME_INTERVAL,    /* Timer interval */
                        SemHandle,        /* Semaphore handle */
                        &TimerHandle)))   /* Timer handle (returned) */
    printf("Recurring timer with %f second interval started.\n",
           TIME_INTERVAL/1000.0);
  /*  */
  for(i=1; i<4; i++)
    if(!DosSemSetWait(SemHandle,             /* Semaphore handle */
                      SEM_INDEFINITE_WAIT))  /* Timeout period -
                                                       indefinite */
      printf("Recurring timer cleared semaphore %d times.\n", i);
  if(!(rc=DosTimerStop(TimerHandle)))        /* Timer handle */
    printf("Recurring timer has been stopped.\n");
}