Stopping countup timer on hitTest?

Hey everyone,
I am working on a project for school which involves developing a timer that counts up to accompany a small game.
My idea involves the timer recording the amount of time taken to complete a small level, and then displaying the
stopped time on the next frame as a final score.

This is the code I used for the countup timer (I am using AS2):

timer = 0;
countup = function() {
timer++;
}

countupInterval = setInterval(countup,1000);

What I want to happen is for the counter to stop once the player reaches a certain object. The hitTest is already
set up on the movie clip of the goal object, using this code (placed on the movie clip):

onClipEvent (enterFrame) {
if (this.hitTest (_root.player)) {
_root.gotoAndStop (2);
}
}

What I cant seem to be able to do is create code that will stop the timer once the player moves over the hitTest,
allowing it to be displayed as a final score on the second frame. I have been researching on many forums and tutorial
sites and have not yet found code so far that works for me in this situation. The project is due a week from now, if
you guys could help me it would be much appreciated ! I can also provide any other additional details that may be needed.

p.s: I am using Flash CS5