Landing URI in Pre Logon

I had this working at one point and I just can't remember the exact flow to the pre-logon sequence. There is a variable for pre-logon that is session.network.server.landing_uri and I just need to know how to incoporate it properly. All I want it to do is to check the landing URI at the beginning of the the prelogon and so if the user types in https://mysite.com/antivirus that it goes directly to the logon page, if they type https://mysite.com they go through the normal checks that we do and get dropped into PWS. I am almost positive I had something like this working before.