EXIT BUTTON Not Working

Hi there...

I am pretty much a newbie working with Flash, so I would really appreciate any kind of help.

I have created a game, with lot of "brain burn" and getting help from the web, however, when I tried to put an exit button, even if I copied the AS3 code, it did not work.

This is what I Have

import flash.events.MouseEvent;

import flash.media.Sound;

import flash.system.fscommand;

fscorea_txt.text = score.toString();

playAgainButton.addEventListener(MouseEvent.CLICK, playAgain);

exitBtn.addEventListener(MouseEvent.MOUSE_DOWN, exitGame);

function exitGame(event:MouseEvent):void {

    fscommand("quit");

}

function playAgain(event:MouseEvent):void {

    playAgainButton.removeEventListener(MouseEvent.CLICK, playAgain);

    gotoAndStop(6);

}

I have also tried with MouseEvent.Click, exitGame but it did not work either, however, the other button works perfectly fine

Any help, please?

Thanks!!!!