Removing (stopping) a function

1

Hello all !
I have a question :h: . I have this function

this.onEnterFrame = function(timer) {
        myTime = getTimer()/1000;
        hours = Math.floor(myTime/3600);
        minutes = Math.floor((myTime/3600-hours)*60);
        seconds = Math.floor(((myTime/3600-hours)*60-minutes)*60);
        mili = Math.floor((myTime-(seconds+(minutes*60)+(hours*3600)))*100);
        myhours = (hours<10) ? "0"+hours : hours;
        myseconds = (seconds<10) ? "0"+seconds : seconds;
        myminutes = (minutes<10) ? "0"+minutes : minutes;
        mymili = (mili<10) ? "0"+mili : mili;
        timerText.text = myhours+":"+myminutes+":"+myseconds+":"+mymili;
};

But i want that when i click a button some text appears in the timerText textfield, i tried that but when i click the button the text just appears a second and then the timer continue. So my question is how can i remove this function, i tried

delete this.onEnterFrame

but i doesn’t work, can someone help me ?
Thanks

Ubik