Again onEnterFrame :(

I want to play sound only one time, and not on each enterFrame, anyone ?


this.onEnterFrame = function() {
    //check voor nieuwe post
    var check1 = _root.nieuw.text;
    var check2 = _root.oud.text;
    //tijd zooi
    var time = getTimer()-startTime;
    var milliseconds = lengte-time;
    var seconds = Math.floor(milliseconds/1000);
    var minutes = Math.floor(seconds/60);
    seconds %= 60;
    minutes %= 60;
    if (seconds<10) {
        seconds = "0"+seconds;
    }
    if (minutes<10) {
        minutes = "0"+minutes;
    }
    alles = minutes+seconds;
    if (alles == 0) {
        _root.play();
    }
    //check nieuwe psot
    if (check1 != check2) {
        sound.play();   //<-that needs to play only one time.  
    }
    timer.text = "refresh @ "+minutes+":"+seconds;
};