Add 10 seconds to timer

programming flash
1

Hi, I have a countdown timer counting down from 60 seconds. What I would like to happen is when the user clicks on the stage I would like the timer to increase by 10 seconds and then carry on counting down.
e.g
The user clicks when the timer is at 45 seconds so then the time jumps to 55 seconds and resumes counting down, whilst the time is displayed in a text box.

I asked in another forum and they pointed me to a link on adobe for the delay property. I gave this a go and I got it to add 10 seconds but then it kept on firing every 10 seconds (as you might expect) but not really what I was after.

I’m new to AS3 so please make any explanation simple, here is the code for the timer.

var count:Number = 60;
var myTimer:Timer = new Timer(1000,count);
myTimer.addEventListener(TimerEvent.TIMER, countdown);
myTimer.start();


function countdown(event:TimerEvent):void {
myText_txt.text = String((count)-myTimer.currentCount);
}

if(myText_txt.text == "0"){
   trace("end")
}

stage.addEventListener(MouseEvent.MOUSE_UP, addTen); 


function addTen(event:Event){
    

 //add ten seconds

 
  
}

Thanks for any help in advance