One Server - Many Web Sites

I deleloped a "template" web site for a national organization. They have 2000 members and wish to offer this site to each member. Some members will have their own domain, others will not. Regardless, each site will be hosted on one server by the organization. Here is the problem I am facing. Yesterday, they did their first test of this template. The client sent me this url - http://www.atra.com/~atra_member

When I went to the address, I noticed any reference in the site to a session variable defined in the global.asa was not showing up. From past experience, I seem to remember that the .asa file needs to be in the root web, yes? Seeing as they will have two thousand of these templates on the same server, how can I achieve what I am trying to do here. I want each site to be easily modified for each client. The only thing that needs to change on each site is address, name, tel., fax, etc. I thought a single global.asa file and session variables would do this hence my approach.