A lookup editor can filter items in its dropdown based on a value in another lookup. This example utilizes the Model-View-ViewModel design pattern to implement cascading LookUpEdit controls. The example binds a child LookUpEdit data source to a collection in a view model that returns a list of business objects depending on a selected object in the master lookup.
Read the following KB article for additional information: MVVM - How to implement cascading LookUpEdits.