Non-repeating animation?

Here’s my dilemma:

Here’s the website I’m working on: www.neuroharvest.com/newsite

What I’d like to do is for each quadrant to have some basic animation (one or two of the neurons in the background would basically outgrow from the brain), which doesn’t seem to be a problem, what I had thought to do originally was when you press on one of the navigation buttons (ie. portfolio) I’d enter in something like

on (release) {
gotoAndPlay(25);
}

which would start a movie clip of some neuron animation in the respective quadrant. the problem I’m running into is I only want that animation to play once (i.e. the first time you enter that quadrant you see that animation, but afterwards, it doesn’t repeat, you just see the finished animation intact)… I apologize if this sounds a little confusing, but in any case, any thoughts?

-Sean