Username from LDAP in proxy request

[Winnicki, Brian (GE, Corporate)]

 Hi,
I'm looking for some help with proxying requests using free-radius.  I
have
a situation where I need to perform a query to an LDAP that contains
both
the back-end authentication server as well as username for a user.  For
example, the User-Name in the originating request may be User1.
FreeRADIUS
then queries LDAP, which contains attributes called authenticationserver
and
authenticationuname.  The authenticationserver is where the request
should
be proxied to, and the authenticationuname is the User-Name that should
be
substituted for the original user-name in the proxy request.  I have the
first part working, where I mapped authenticationservername to
Proxy-To-Realm in the ldapmap file.  I also setup all the possible
values as
realms.  The server is now forwarding requests based on what it gets
back in
the LDAP query.  I'm stuck however at trying to substitute the User-Name
from what is retrieved from LDAP.
Anybody know anyway to do this?