Help on : tree-view-update-item function

Hi guys

I am stuck in a very simple piece of code and need help.

(defclass MyTreeNode ()

(( ... )))

(setq RootNode (make-instance 'MyTreeNode ...))

(setq TV (make-instance 'tree-view :roots (list RootNode)))

(contain TV)

Till here the tree-view is opened with the RootNode in it.

When the user clicks on the right mouse button I open a popup

me nu and add a child to the RootMenu. Now I need to update

the RootMenu in the tree-view to include the newly created

child for RootMenu.

(assert (typep arg1 'MyTreeNode))

(assert (typep arg2 'tree-view))

(tree-view-update-item arg2 arg1 nil) ;*** throws an exception

Please can you tell me why is the tree-view-update-item not working?

Ismail