WPF List View Binding - Newbie

Question

I have bound a object to a listview but it seems I can only sort fields of my object.
I have a custom converter tied to a few fields. Is there any way to sort these fields or fields that aren't properties. I'm using sortdescriptions and binding to a tag field in the gridview columns so I have no trouble sorting properties.

Thanks in advance!!!

Let me know if you need more info. I've spent hours trying to find this out.