[FLASH 8] MC position's changing at first Zoom attempt

///ZOOM///
myZoom = function (myDepth)
{
    if (myDepth == "deep")
    {
        myDepth = 4;
    }
    else if (myDepth == "medium")
    {
        myDepth = 8;
    }
    else if (myDepth == "light")
    {
        myDepth = 12;
    } // end else if

    img.onRelease = function()
    {
        if (k > 0)
        {
            return;
        } // end if
        zoom = true;
        dir == 1 ? (dir = -1) : (dir = 1);
        if (dir == 1)
        {
            pt = {x: img._xmouse, y: img._ymouse};
        } // end if
    };
    this.onEnterFrame = function ()
    {
        if (!zoom)
        {
            return;
        } // end if
        img._xscale = img._xscale + dir * k * 50 / myDepth;
        img._yscale = img._yscale + dir * k * 50 / myDepth;
        var pt2 = {x: pt.x, y: pt.y};
        img.localToGlobal(pt2);
        img._x = img._x - (pt2.x - pt.x);
        img._y = img._y - (pt2.y - pt.y);
        ++k;
        if (k == 8)
        {
            zoom = false;
            k = 0;
        } // end if
    };
};
myZoom("medium");
///END ZOOM///