selective disabling password logging for proxied users?

Hello, I'm sorry, that I ask again .. We are using the freeradius server with authentication against ldap as "local database" and proxy the realms (IPASS) to authenticate users are not in our database. So is is possible, to disable the password logging only for the proxied request? The local requests are only users who got a temporary voucher. In case of failure, the help desk should use the log to check if the user did use the correct password. But the password for IPASS users password should not be logged. If I disable the password logging in the detail section (suppress {User-Password}), the complete password logging will be disabled. Is it possible, to disable this selective only for proxied users? Thanks for help - Meike