Either you use a module with alarm functionality (which polls the time for you) or you poll the clock yourself...then DO_EVENTS so the system can do stuff...then poll again to see if current_time - last_event_time >= period. If you want this code to be "fairly" reliable in timing, make it a service with the win32 service module. But even a service can be delayed for a long time, eg system decides to increase size of swap file etc. If you want guaranteed n calls to periodic_procedure for n seconds with little or no latency, then Real Time OS to start with is your only option in my opinion. Chris