Web-control with collections with "many to many" relation?

Question

Hello! I have three collections(that derive from CollectionBase): Coll1: Holds the master objects Coll2 Holds the relations of Coll1 and Coll3 objects(like this: Coll2[i].master and Coll2[i].child) Coll3 Holds the child objects So the Coll1 and Coll3 have many to many relationship. Databinding one collection to a web-user control like listbox is easy but how can I represent the relations within these collections? For example if I want to show the master objects in listbox1 and when object is clicked, show the child objects related to this master object in listbox2. How can I create the relation? Thanks in advance, Kerkkoj.