How do I know whether the tree is loaded completely

Suite and Optimus Suite 5
#1 
var tree = null;
function createMenuTree(){
	//alert('createMenuTree');
	tree=new dhtmlXTreeObject("menuTree","100%","100%",0);
	tree.setSkin('dhx_skyblue');
	tree.setImagePath("../images/dhtmlxtree/");
	tree.enableDragAndDrop(0);
	tree.enableTreeLines(true);
    tree.setImageArrays("plus", "plus2.gif", "plus3.gif", "plus4.gif", "plus.gif", "plus5.gif");
    tree.setImageArrays("minus", "minus2.gif", "minus3.gif", "minus4.gif", "minus.gif", "minus5.gif");
    tree.setStdImages("book.gif", "books_open.gif", "books_close.gif");
	tree.loadXML("../tree/menuTree.xml");

     var firstId = tree.getSelectedItemId();//here...
	alert(firstId);// ""
}

in menuTree.xml, a childItem is selected: .
now I want to get this selected Item id,but it return “” in alert window, so How should I do? is there a loadComplete Event or something like this? hope someone can provide me the event list of dhtmlxtree or some other solutions.
regartds,

#2

You can use “onXLE” event

#3

very good, it works.Thanks a lot~