realm question

Hi there, I have a question about prefix realms and stripping them. I have a provider that allows roaming dialup for our customers. They require the username to be in a format of idm/something/username. I get the whole idm/something/username delivered to me as the authentication. I have tried using the IPASS prefix to remove the idm/something, but it just returns the realm of idm and I am still left with stripped-user-name of something/username, I have also tried just adding a realm of "idm/something" to the proxy.conf and it didn't work. I am currently running freeradius 2.0.5 with a SQL (mysql) back end. Can I strip the "idm/something/" somehow? Thanks, Jeff.