radius proxy senario

[piston]

Hi

I need some opinions.

Condition:

1. I have a local realm (suffix), xyz.com. I'm using freeradius 2.1.3+mysql.

2. My own user's username in mysql radcheck table is store in username at xyz.com format

3. A person want me to proxy his prefix ABC/his-customer-username at myrealm to his radius server, i.e: ABC/his-customer-username at xyz.com

4. The proxy has strip both prefix and suffix, which means when ABC/his-customer-username at xyz.com auth request come in, i have to forward only his-customer-username to his radius.

I know i can using hint to strip his prefix, but i'm stuck at proxy config. I can't proxy xyz.com to his radius, otherwise my own user's username will also proxy to his radius server.

How can i proxy his-customer-username without mess up my own user's username?  

It's sound a bit stupid, but i still keen to find out is that possible to achieve the objective or not.

Thanks a lot!!

Piston