How to stop a timer from another class?

Hi I'm trying to stop a timer in stopwatch class from MainMenu class. But my code doesn't work, here is my code:

in MainMenu class i've method:

public function pauseGame (e:MouseEvent){ 
     timestop = new Stopwatch(); 
     timestop.Stoptimer(); }

in class Stopwatch i try to stop my timer with:

 public function Stoptimer(){ 
      timer.stop(); 
      timer.removeEventListener(TimerEvent.TIMER, timeFun);
      return; }