How to bind listbox dynamically with hierarchical mode in silverlight 4

Hi,

   Today i have given a task and need to complete it by the end of the day. I have two listbox with drag drop options. the first list box contains "Users"  and the second listbox contain "permission" . I have a third listbox that should be bind dynamically in hierarchical mode. Like "users" have different permission.

Example:

              Admin
                        Master menu
                        Control Menu
                User
                       Control Menu
And this should be done dynamically. from first listbox i will drag and drop to third listbox. from the second listbox i will drag and drop as a sub menu to first listbox item.

 Please help me out.....

Thanks,
Vijay