Refreshing a Tree Control after nodes are added using Ajax

Hi Folks,
I am facing an issue when refreshing the tree.

Here is how I am creating tree. For the first 3 initial levels of data in the tree, its a one time fetch. When the user clicks on any of the leaf nodes, I use the AW.HTTP.Request class to retrieve the data from the back end and populate the leaf node with the values retrieved. They now appear as children of the leaf.
Problem is after the values get retrieved the data is not visibly available below the leaf node.

I used obj.refresh() to refresh. But nothing seems to work.

Please Help...!!!!!

Regards
Jaydeep