Whats the time?

programming flash
1

Hey
this works well but I have one wee question. once the variable hits 60 seconds how do I tell it to display minutes:seconds.
rather than just seconds??

var time_Duration:Number;
var total_frames = _root._totalframes;
var the_currentFrame =_root._currentframe ;
onEnterFrame = function(){
var the_currentFrame =_root._currentframe ;
time_Duration = Math.floor(the_currentFrame/30);
trace(time_Duration);
}