CalledStationID

I'm trying to solve a design issue and wonder if anyone has done something similar with hotspots. I would like to send back different values in the VSAs when a user logs in from one calledStationID vs another. For example. User joe logs in from hotspot1. the calledStationID is sent. FreeRADIUS takes that and sends back the local DNS server IP address (or whatever is specific to that region) instead of the one tied to, say, hotspot100. The goal is to allow me to setup different regions in FreeRADIUS with region-specific parameters. I had some things that I thought would work, but I'm wondering how others have solved this problem. Jeffrey