I have a MOSS 2007 site and a couple different subsites. I want to set up the subsites so that, if you don't have access, you can request it. If you do already have access, you go right to the subsite.
On the Home site, I have a link in the left-hand NavBar. When they click the link they should go to the subsite if they already have access. If they don't, they fill out a short survey (with name, phone, etc) so that we can grant them access. After that, we can drop them back at the 'home' page.
EDIT: I don't have access to the web.config or any back-end settings. I'm an admin for a site that is part of a much larger group of sites.