[Zope] tree structure

Hi, I am sending a variable say userid with it's value as hidden as the root of the tree to the next page where the code for the tree structure is written.The tree structure page displays the branches of root(this value had come as hidden by the name userid) but i can't expand further. It says Error value : userid (the variable which had come has hidden). To be clear i want to build a hierarchy of people taking Employee No as the id. please throw some light. Thanks, jacintha