radwho and location

Hi All, I've just started with FreeRADIUS and noticed that when running radwho the 'location' field seems empty. (FreeRADIUS 2.1.7 from the source on Ubuntu 8.04LTS) There doesn't seem to be a configuration option/tweak anywhere I can find, or am I missing something? The reason I'm interested is that we're wanting to limit simultaneous-use on some kind of 'grouping' not per-unique-username and I'm wondering if radwho/location might be an obvious place to track that (if I could just work out how to get the info in there). Thanks, Phil P