var my_xml:XML = new XML();

my_xml.load("myxml.xml");

var checkLoadXML = function (xmlObj:XML) {

        preloader_mc._visible = true;

        var bLx:Number = xmlObj.getBytesLoaded();

        var bTx:Number = xmlObj.getBytesTotal();

};

my_xml.onLoad = function(suc:Boolean) {

        clearInterval(intervalID);

};

var intervalID:Number = setInterval(checkLoadXML, 100, my_xml);