hey hai,
i just created a new sample block according to the instructions that are given in moodle.org.
i opened a yui docs files in that i got a code for a tree view that is
YUI().use("yui2-treeview", function(Y)
{
var YAHOO = Y.YUI2;
var treeView = new YAHOO.widget.TreeView("treeContainer");
treeView.render();
});
name this file with the extention .js
and write a un ordered list put that in div tag.
give the id=treeContainer for that div tag, now the tree view is ready.
respect to your unordered list,
style it according to your layout format
here the nav_tree.js is above code
thanks