Set constant on GO created by factory

I have another thread about passing data to GO:s loaded by Collection Proxies. I have not found a simple way of doing it.
Someone suggested I have the instantiated GO send it’s url to the main controller, and that works well. Kind of like an event listener.
But it would be easier to just have the option to include a context object that get passed to the collection GO:s.
I’m not sure what the difference is between “loading” and “instantiating”, apart from the reference counting that enables “unload”. In my case the loading of the collection results in it being instantiated, doesn’t it? I’m only using the Collection Proxy because I want to be able to Unload easily.