Removing movieclip/jumping flash site

i have a game with a timer that goes from 30 to 0, if u finish the game before 0, u win and get to the “you won” frame, and from there I want to go to the menu. but let’s say it’s 10 seconds left on the clock when u finish, then if i press the “back” button, it just quickly goeas back to the menu, before it jumps to the “you won” frame again. and I noticed it’s doing that every second, and when the timer should be at 0 it works again, i get to the menu.
so basically i have to deactivate the timer when i get to the “you won” frame. how do i do that with this?

function countDown(){
    _root.timeLeft.text = --countTotal;
    if(countTotal <= 0){
    if(score == 50){