How can I bind NSButtonCells title to a controllers arrangedObject?

Question

Hello,

I have an OutlineView with one column of NSButtonCell checkboxes. The content binding of the outline view is to a TreeController. Currently, I can bind the checkbox status to the content of the TreeController by binding the value of the Table Column to TreeController.arrangedObjects.shouldBeCopied. However, I can only seem to bind the title text for the NSButtonCell from the Cells own properties and I've set this to TreeController.arrangedObjects.nodeTitle but this doesn't work, I just get blank titles.

Have I set up the OutlineView incorrectly in that I have to bind the Columns not the Cells or am I binding to the wrong property? The nodeTitle property is fine as I've tested it out with a normal text cell instead of the checkbox.

Thanks.