separately logging of multiple conditionals

Hello, Is is possible to include multiple separated linelog calls in different exceptions of single virtual server? Goal is to catch authenticated user-names, separately, depending on various addressed proxy servers (realms). I tried also detail.log pre_proxy_log, but it might be tedious to work with later on. Alternatively is there a way to write addressed proxy server to authentication log or linelog? Best regards, Bartek Chmielewski