LDAP Quesion

OK this is a question coming from a very very newbie in the F5 network... Lets see how I can state this... What I am training to do is when a user hits my VIP depending on the URI say if they hit /mypage/auth/ they get prompted for LDAP authentication... however if they hit any other page that isn't below the /mypage/auth/ directory they don't get authenticated and are accessing the site via anonymous... Now would that be better to setup in IIS or should I setup an iRule of some sort to process the LDAP authentication? If iRule is suggested... Anyone got any pointer's on how to setup LDAP for MS AD?