Set and get of htmlb tree

How do i get the Tree node component in JSPDynpage?

If i use,

TreeNode tn = (TreeNode)this.co........ByName("node1");

I get an error: cannot cast the component to TreeNode.

Iam trying to set values through the set methods of the tree on JSP.

I want the Treenode to be open even after clicking the node.

Ex:Access a node and then

set.Open(true) of that node ..in itz method on Dynpage.

Thanks for all the hints!