How do I simulate clicking on a tree node?

This seems very basic, but I can't figure it out. How can I simulate (in javascript) clicking on a tree node (for a given index value) with the result that the tree expands with that node selected?

Thanks.

http://www.activewidgets.com/javascript.forum.10102.9/tree-control-suggestion.html
<script>

var tree = {
0: [1, 2, 3, 4],
1: [5, 6],
2: [7],
3: [8],
4: [9]
}

var obj = new AW.UI.Tree;
obj.setItemText(["", "Home", "Favorites", "Font size", "Search", "Child node 1", "Child node 2"]);
obj.setItemImage(["", "home", "favorites", "fontsize", "search"]);
obj.setViewCount(function(i){return tree[i] ? tree[i].length : 0});
obj.setViewIndices(function(i){return tree[i]});
document.write(obj);

obj.onItemClicked = function( event, row){
var state = obj.getViewExpanded(row);
if (state == true) {
obj.setViewExpanded(false, row); }
else {
obj.setViewExpanded(true, row); }
}

var button = new AW.UI.Button;
button.onControlClicked = function(){obj.onItemClicked(null,3)}
document.write(button );

</script>