Scrolling X not Y

[m_h_w]

Working with this code from a tutorial:

import mx.transitions.Tween;
import mx.transitions.easing.*;

var myGalleryXML = new XML();
myGalleryXML.ignoreWhite = true;
myGalleryXML.load("gallery.xml");

myGalleryXML.onLoad = function() {
    _root.gallery_x = myGalleryXML.firstChild.attributes.gallery_x;
    _root.gallery_y = myGalleryXML.firstChild.attributes.gallery_y;
    _root.gallery_width = myGalleryXML.firstChild.attributes.gallery_width;
    _root.gallery_height = myGalleryXML.firstChild.attributes.gallery_height;

    _root.myImages = myGalleryXML.firstChild.childNodes;
    _root.myImagesTotal = myImages.length;

    _root.thumb_height = myGalleryXML.firstChild.attributes.thumb_height;
    _root.thumb_width = myGalleryXML.firstChild.attributes.thumb_width;

    _root.full_x = myGalleryXML.firstChild.attributes.full_x;
    _root.full_y = myGalleryXML.firstChild.attributes.full_y;

    callThumbs();
    createMask();
    scrolling();

};

function callThumbs() {
    _root.createEmptyMovieClip("container_mc",_root.getNextHighestDepth());
    container_mc._x = _root.gallery_x;
    container_mc._y = _root.gallery_y;

    var clipLoader = new MovieClipLoader();
    var preloader = new Object();
    clipLoader.addListener(preloader);

    for (i=0; i<myImagesTotal; i++) {
        thumbURL = myImages*.attributes.thumb_url;
        myThumb_mc = container_mc.createEmptyMovieClip(i, container_mc.getNextHighestDepth());
        myThumb_mc._y = _root.thumb_height*i;
        clipLoader.loadClip("thumbs/"+thumbURL,myThumb_mc);

        preloader.onLoadStart = function(target) {
            target.createTextField("my_txt",target.getNextHighestDepth(),0,0,100,20);
            target.my_txt.selectable = false;
        };


        preloader.onLoadProgress = function(target, loadedBytes, totalBytes) {
            target.my_txt.text = Math.floor((loadedBytes/totalBytes)*100);
        };

        preloader.onLoadComplete = function(target) {
            new Tween(target, "_alpha", Strong.easeOut, 0, 100, .5, true);
            target.my_txt.removeTextField();
            target.onRelease = function() {
                callFullImage(this._name);
            };

            target.onRollOver = function() {
                this._alpha = 50;
            };

            target.onRollOut = function() {
                this._alpha = 100;
            };


        };
    }
}



function callFullImage(myNumber) {

    myURL = myImages[myNumber].attributes.full_url;
    myTitle = myImages[myNumber].attributes.title;
    _root.createEmptyMovieClip("fullImage_mc",_root.getNextHighestDepth());
    fullImage_mc._x = _root.full_x;
    fullImage_mc._y = _root.full_y;

    var fullClipLoader = new MovieClipLoader();
    var fullPreloader = new Object();
    fullClipLoader.addListener(fullPreloader);

    fullPreloader.onLoadStart = function(target) {
        target.createTextField("my_txt",fullImage_mc.getNextHighestDepth(),0,0,200,20);
        target.my_txt.selectable = false;
    };

    fullPreloader.onLoadProgress = function(target, loadedBytes, totalBytes) {
        target.my_txt.text = Math.floor((loadedBytes/totalBytes)*100);
    };

    fullPreloader.onLoadComplete = function(target) {
        new Tween(target, "_alpha", Strong.easeOut, 0, 100, .5, true);
        target.my_txt.text = myTitle;
    };

    fullClipLoader.loadClip("full_images/"+myURL,fullImage_mc);

}

function createMask() {

    _root.createEmptyMovieClip("mask_mc",_root.getNextHighestDepth());

    mask_mc._x = _root.gallery_x;
    mask_mc._y = _root.gallery_y;

    mask_mc.beginFill(0x000000,100);
    mask_mc.lineTo(_root.gallery_width,0);
    mask_mc.lineTo(_root.gallery_width,_root.gallery_height);
    mask_mc.lineTo(0,_root.gallery_height);
    mask_mc.lineTo(0,0);

    container_mc.setMask(mask_mc);

}

function scrolling() {
    _root.onEnterFrame = function() {

        container_mc._y += Math.cos(((mask_mc._ymouse)/mask_mc._height)*Math.PI)*15;

        if (container_mc._y>mask_mc._y) {
            container_mc._y = mask_mc._y;
        }

        if (container_mc._y<(mask_mc._y-(container_mc._height-mask_mc._height))) {
            container_mc._y = mask_mc._y-(container_mc._height-mask_mc._height);
        }

    };
}

What is does is create a photo gallery. In this case the thumbs are scrolling on a Y axis. while i want them to scroll on a X axis. Been playing around with the code but havent really achieved the result i want.

Source code an files here:
http://www.republicofcode.com/tutorials/flash/xmlimagegallery/source.zip