Move dynamic mask movie.. with Mouse movement

1

Hi everyone, hi like to move my masked dynamic menù, at right and left by mouse move on mask area. I’ve use an conditions to force the sliding but it doesnt work fine. My mask area is large 973 px

This is the code i ve.

MovieClip.prototype.easeX = function(x) {
    this.onEnterFrame = function() {
        this._x = x-(x-this._x)/1.2;
        if (Math.abs(x-this._x)<=1) {
            //delete this.onEnterFrame;
            this._x = x;
        }
    };
};


this.onEnterFrame= function() {
        if (_root.mask.hitTest(_root._xmouse, _root._ymouse)) {
            slideMenu();
        }
    };


slideMenu = function () {
    if (_root._xmouse>782) {
        this.container.easeY(-214);
    } else {
        this.container.easeY(88);
    }
};

Anyone can help me??