IIS equivalent for Apaches httpd.conf servername

I'm working with a hardware loadbalancer to redirect to 24 different
machines.

I use Apache on 12 of them and IIS on the other 12. On the Apache
machines Servername is set to the url that users type in their
browser. So each redirected session has the same url for the user.

I would like to have the servername functionality on my IIS server
also, but I am not a real IIS specialist, tryed different things but
nothing works. Does anybody know the answer to this simple problem?

Thx, raoul