Modifying the kirupa thumbnail scroller for gallery?

I am looking to modify the kirupa thumbnail scroller. It just doesn’t work as smoothly and as well as I would like.

I simply would like to have two buttons that make the thumbnails slide in the correct directions. Here is my code so far.

    scroll_speed = 5;
    tscroller.onEnterFrame = function() {
        if (thumbnail_mc.hitTest(hit_right)) {
            hit_right.onRelease = function() {
                thumbnail_mc._x -= scroll_speed;

As you can probably guess, it only works once. It moves the scroller once, not continuously. I though the onEnterFrame would have taken care of that but I guess not.

Any thoughts please?