Center external menu in flash

Hello there!I bought a flash template and i try to change it.My problem is that i cannot center my main menu when i resize the .swf file.

My menu is read from an external .xml file from where it takes the menu values (i.e. Main | Contact | Fotos etc).

At my .fla file at the loadmainmenu - movieclip i can see only one dynamic text and a seperator - which are probably populated through a function. At this movie clip it has no code.

At the main clip it has a layer named functions where it contains code, in which i saw this part:

function clearMainMenu () {

for (a = 0; a < xmlTotalItems; a++) {
    nav_menu.attachMainMenu["mainMenuItem" + a].menuTitle._tint = 0x707070;
    nav_menu.attachMainMenu["mainMenuItem" + a].bt.enabled = true;
}
thisNav = undefined;

}
//
function loadMainMenu () {

var mainMenu:XML = new XML ();
mainMenu.ignoreWhite = true;

mainMenu.onLoad = function (success) {
    if (success) {

        var xml:XMLNode = this.firstChild;
        xmlTotalItems = xml.childNodes.length;
        for (i = 0; i < xml.childNodes.length; i++) {
            var itemTitle:String = xml.childNodes*.childNodes[0].childNodes[0].nodeValue;
            var itemContent:String = xml.childNodes*.childNodes[1].childNodes[0].nodeValue;

            nav_menu.attachMainMenu.attachMovie ("mainMenuItem","mainMenuItem" + i,i);

            nav_menu.attachMainMenu["mainMenuItem" + i].menuTitle.txt.htmlText = itemTitle;
            nav_menu.attachMainMenu["mainMenuItem" + i].menuTitle.txt.autoSize = true;

            if (i == 0) {
                nav_menu.attachMainMenu["mainMenuItem" + i]._x = i;
                nav_menu.attachMainMenu["mainMenuItem" + i].tabs._x = nav_menu.attachMainMenu["mainMenuItem" + i].menuTitle._width + 15;
                nav_menu.attachMainMenu["mainMenuItem" + i].bt._width = nav_menu.attachMainMenu["mainMenuItem" + i].menuTitle._width;
            }
            else {
                nav_menu.attachMainMenu["mainMenuItem" + i]._x = nav_menu.attachMainMenu["mainMenuItem" + (i - 1)]._x + nav_menu.attachMainMenu["mainMenuItem" + (i - 1)]._width + 15;
                nav_menu.attachMainMenu["mainMenuItem" + i].bt._width = nav_menu.attachMainMenu["mainMenuItem" + i]._width;
                if (i == xmlTotalItems - 1) {
                    nav_menu.attachMainMenu["mainMenuItem" + i].tabs._visible = false;
                }
                else {
                    nav_menu.attachMainMenu["mainMenuItem" + i].tabs._x = nav_menu.attachMainMenu["mainMenuItem" + i].menuTitle._width + 15;
                }
            }
            nav_menu.backMenu_center._x = nav_menu.backMenu_left._x;
            nav_menu.backMenu_center._width = nav_menu.attachMainMenu._width;
            nav_menu.backMenu_right._x = nav_menu.attachMainMenu._x + nav_menu.attachMainMenu._width;

            nav_menu.backMenu_left._alpha = 35;
            nav_menu.backMenu_center._alpha = 35;
            nav_menu.backMenu_right._alpha = 35;

            nav_menu.attachMainMenu["mainMenuItem" + i].bt.instance = i;
            nav_menu.attachMainMenu["mainMenuItem" + i].bt.instanceText = itemContent;

            nav_menu.attachMainMenu["mainMenuItem" + i].bt.onRollOver = nav_menu.attachMainMenu["mainMenuItem" + i].bt.onDragOver = function () {
                ZigoEngine.doTween (this._parent.menuTitle,'_tint',websiteColor,0.5,"easeOutExpo");
            };
            nav_menu.attachMainMenu["mainMenuItem" + i].bt.onRollOut = nav_menu.attachMainMenu["mainMenuItem" + i].bt.onDragOut = function () {
                ZigoEngine.doTween (this._parent.menuTitle,'_tint',0x707070,0.5,"easeOutExpo");
            };
            nav_menu.attachMainMenu["mainMenuItem" + i].bt.onRelease = function () {

                lastSubNav = undefined;
                thisSubNav = undefined;

                lastNav = thisNav;
                thisNav = this.instance;

                ZigoEngine.doTween (this._parent.menuTitle,'_tint',websiteColor,0.5,"easeOutExpo");
                ZigoEngine.doTween (nav_menu.attachMainMenu["mainMenuItem" + lastNav].menuTitle,'_tint',0x707070,0.5,"easeOutExpo");

                nav_menu.attachMainMenu["mainMenuItem" + lastNav].bt.enabled = true;

                this.enabled = false;

                if (this.instanceText == "submenu") {
                    ZigoEngine.doTween (nav_menu,'_y',Stage.height,0.5,"easeOutExpo");
                    if (subMenuOpened == true) {
                        ZigoEngine.doTween (nav_menu,'_y',Stage.height + 25,0.5,"easeOutExpo",0,function () {
                        ZigoEngine.doTween (nav_menu,'_y',Stage.height,0.5,"easeOutExpo");
                        subMenuOpened = true;
                        loadSubMenu ();
                        });
                    }
                    else {
                        subMenuOpened = true;
                        loadSubMenu ();
                    }
                }
                else {
                    subMenuOpened = false;
                    ZigoEngine.doTween (nav_menu,'_y',Stage.height + 25,0.5,"easeOutExpo");
                    closeAudioPlaylist._height = Stage.height - 95;
                    swfToOpen = this.instanceText;
                    content_blocker._visible = true;
                    ZigoEngine.doTween (content_container,'_alpha',0,0.5,"easeOutExpo",0,function () {
                    loadMovieClip (swfToOpen,content_container);
                    });
                }
            };
        }
    }
};
mainMenu.load ("xml/website_contents.xml");

}

in another layer named config i found this piece of code for placing to center a small logo:

function loadLogo (externalTarget:String, targetRoot:MovieClip, action:String) {

var mcLoader:MovieClipLoader = new MovieClipLoader ();
var listenerLoad:Object = new Object ();

listenerLoad.onLoadStart = function (target:MovieClip) {
    targetRoot._alpha = 0;
    isLoading = true;
};
//On Load Complete
listenerLoad.onLoadInit = function (target:MovieClip):Void  {

    if (action == "ini") {
        ZigoEngine.doTween (targetRoot,'_alpha',100,3,"easeOutExpo");
    }
    target.onRelease = function(){
        ZigoEngine.doTween (content_container,'_alpha',0,0.5,"easeOutExpo",0,function () {
            loadMovieClip (defaultHomepage,content_container);
            clearMainMenu ();
        });
    }
    //Center position of the small logo considering an area of 160x75px 
    target._x = 160 / 2 - target._width / 2;
    target._y = 75 / 2 - target._height / 2 - 100;
    
    isLoading = false;
};
mcLoader.addListener (listenerLoad);
mcLoader.loadClip (externalTarget,targetRoot);

}

How could i make my external menu to be placed at center while resizing?Where to put the code?(When i say center i mean at the center of the width of main movie(not center height also).

Thank you in advance