realm rewrite or alias?

Hello everyone, I've got FreeRADIUS running to proxy requests from a wireless controller to a domain controller (NPS). The realm name is being passed to NPS as the logon domain, which is fine but I'd like to catch a number of different possible realms that users may put into the login and 'rewrite' them to the proper domain name so that the domain controller doesn't reject the login and we get fewer helpdesk calls. After looking through the config files an doing a bit of searching online I still haven't found a way to do that, is it possible? Beau