CoreData bindings for NSPopupButton

I'm looking to use a dropdown menu (possibly an NSPopupButton object) to represent the hierarchical results of two Core Data entities (Genre and Movie) and their relationships. In my current data model, my Genre entity has a one-to-many relationship with my Movie entity.

What I'm now looking to do is generate the contents of an NSPopupButton to show a hierarchical list of Genres and the Movies associated with them, like so:

Genre 1
    Film 1
    Film 2
Genre 2
    Film 3
    Film 4

Note that, in the开发者_StackOverflow社区 above example, only Movie objects are to be selectable by the user (Genre objects will appear, but be unselectable). Also, to complicate matters slightly, I have an additional NSPopupButton which lists Movie Rental locations. The location selected by the user ultimately impacts on the genres and films available in the second dropdown.

I imagine that bindings will only take me so far with this problem and that, ultimately, I'll have to populate the contents of the dropdown menu myself. I'm posting here for thoughts and opinions on the best way to go about this.