pam_radius can't do that. I have patches which should make this work, which I could send you. But the configuration is quite complex. You may not be up to the task if you're not able to debug your more basic setup.
You should try running radiusd with -X to get useful debug information.
Can you least share some of your insight? This is typical setup, but I have not been able to get CentOS4.2 PAM to use pam_radius for authentication. Currently I am able to use RADIUS to AAA most of the network devices, but want to also AAA linux ssh login as well without success. I have ran the RADIUS with -X option, but have not even seen the traffic on the RADIUS server. Only logs I have been able to locate were on the client server's messages. Even though I was able to compile pam_radius_auth.so on CentOS server, it is suspect. I am pretty sure, if you give me enough information I should be able to follow most complex setup on Linux. InCho