How to reset my Timer

Hello!

I have a question and I hope I can find a solution here.I have a short quiz and I want to allow the user only 30 seconds per question to give a right answer.

I have a "start" button that triggers a countdown timer for the first time. Then, I want each time the user clicks  the button "next", the countdown to start again counting from 30 to 0. This is what I have tried so far:

var fl_SecondsToCountDown:Number = 30;

var fl_CountDownTimerInstance:Timer = new Timer(1000, fl_SecondsToCountDown);

fl_CountDownTimerInstance.addEventListener(TimerEvent.TIMER, fl_CountDownTimerHandler);

start_btn.addEventListener(MouseEvent.CLICK,startCountdown);

next_btn.addEventListener(MouseEvent.CLICK, goNext);

function fl_CountDownTimerHandler(event:TimerEvent):void

{

          seconds_txt.text = String(fl_SecondsToCountDown);

          fl_SecondsToCountDown--;

}

function startCountdown(e:MouseEvent):void{

          fl_CountDownTimerInstance.start();

}

function goNext(e:MouseEvent):void{

                    fl_CountDownTimerInstance.reset();

}

Now, what it does it's just stopping the countdown at 25 seconds, for example, and then if I ask it to start again, it starts where it has left off, instead of going back to 30 seconds again.

Thanks a lot!