Using the timer.device is very easy and allows more control than just using f.e. Delay() or usleep().

There is documentation and examples on how to use it here:
http://wiki.amigaos.net/index.php/Timer_Device

It is explained in the link I posted.

Generally you would do it something like this:

uint32 wait_on_signals; // signals to wait for
uint32 signals; // signals received
 
wait_on_signals = other_signals | timer_signal;
 
StartTimer(timer_io);
 
while (!done) { // program main loop
    signals = IExec->Wait(wait_on_signals);
 
    if (signals & timer_signal) {
        IExec->WaitIO(timer_io);
        StartTimer(timer_io);
        CallFunction();
    }
 
    /* add code for handling other signals here */
}
 
AbortTimer(timer_io);

The StartTimer would set up the TimerRequest for the delay you want and then call IExec->SendIO() to start the timer request while AbortTimer() after the loop would just call IExec->AbortIO() and IExec->WaitIO() to stop and cleanup the remaining timer request so you can free the TimerRequest without worries later.