Hi there! I'm using two entities A and B with to-many-to-many relationship. Lets say I got an entity A with attribute aAttrib and a to-many relationship aRelat to another entity B with attribute bAttrib and a to-many relationship bRelat with entity A. Now I am building an interface with two tables one for entity A and another for entity B. The table for entity B has two columns one for bAttrib and one for the relationship aRelat. The aRelat-column should be a NSPopupButtonCell to display multiple aAttrib values. I'd like to set all the bindings in InterfaceBuilder in Table Column Bindings: -- I have two NSArrayController each for one entity: Object Controller Mode:Entity Array Controller Bindings: Parameters Managed Object Context bind to File's Owner -- One Table Cloumn with a PopUpButtonCell: TableCloumnBindings Content bind to Entity A with ControllerKey arrangedObjects; Content Values bind to Entity A with ModelKeyPath aAttrib Selected Object bind to Entity B with ModelKeyPath bRelat I know that this configuration doesn't allow multiple value setting. But I don't know how to do the right one. Getting the following message: HIToolbox: ignoring exception 'Unacceptable type of value for to-many relationship: property = "bRelat"; desired type = NSSet; given type = NSCFString; value = testValue.' that raised inside Carbon event dispatch... Does anyone have any idea?