cocoabinding a nstableview nested in nscollectionviewitem

I have a working Core Data app and I want to display a representation for some of the Entities. I have set up an NSCollectionView with the Interface Builder "Core Data Entity Assistant" to setup the collection (generated a View in the MyDocument.xib), and can access simple representedObject.attributes, as well as simple relationship attributes.

my problem is with the to-many Relationships, which I would like to display as tables nested in the Collection item. I have tried different representedObject keypath combinations for the NSTableColumns, but did not figure out the correct cocoa binding incantation to drill down the data.

EntityA (reprensented in the Collection) <WORKS>
. EntityB (simple relationship) <WORKS with representedObject.relationship.attr>
.. EntityC (to-many-relationsip of EntityB) <how to get there???>

as of right now 99% of the code is generated through the Core Data Model and by Interface Builder. I am not opposed to subclassing something to get the desired behavior but I would prefer to keep things as automated as possible -- especially since this should "just work" with the as-is classes. using Xcode 3.2.开发者_JS百科5 -- I don't mind jumping to 4GM if someone tells me the bindings are more explicit there.