This is how you would use Timer as a setTimeout. The variable tTimer is set to launch 500 ms after start() is run. It will run once and then stop.
private function Timer_example()
var tTimer:Timer = new Timer(500, 1);
private function onTimer(event:TimerEvent)
trace('callback event has run');
Timer can also function like setInterval. The second parameter tells timer how many times it should run. So if you want something to run 100 times then set timer will look like this.
var tTimer:Timer = new Timer(500, 100);
If you want it to run forever then set the interval to 0. If you do this make sure the timer is a global variable so you can run .stop() when it no longer needs to run.