Accessing Joined Table in Flex Viewer

I'm trying to add a field from a JOINED table to the list in the info window from a layer of type "feature" using the Attachment Relate Info Widget. The field does not show up in the window, I just get "undefined" in the info window. I have tried using the field name from the join table as well as the entire table and field name.

From everything I've read about this widget and others, I am not sure if this is possible or not. Anyone have an idea? Thanks, and I apologize if this has been answered, I haven't found it if it has.

Thanks!