Vista - redirect based on URL entered

I have a website that has some issues depending on what URL a user
uses. If they type in http://www.url.com it works fine. If they go
to http://url.com it has issues. This is the issue with two URL's on
the same IIS instance. How would you do the following?

if <URL entered to get here> = "url1.com" go to http://www.url1.com
else if <URL entered to get here = "www.url1.com" go to http://www.url1.com
else if <URL entered to get here> = "url2.com" go to http://www.url2.com
else if <URL entered to get here = "www.url2.com" go to http://www.url2.com

Again thinking some kind of asp/aspx page that needs to run in IIS.
Any ideas?

Thanks.

JR

Slight correction as this would endless loop:

if <URL entered to get here> = "url1.com" go to http://www.url1.com/home2.asp
else if <URL entered to get here = "www.url1.com" go to http://www.url1.com/home2.asp
else if <URL entered to get here> = "url2.com" go to http://www.url2.com/home2.asp
else if <URL entered to get here = "www.url2.com" go to http://www.url2.com/home2.asp

JR wrote:You need to state *exactly* what those issues are. We can't see your monitor
from here...
I suspect that either you haven't set up DNS for both URLs or you haven't
set the host headers for both URLs in IIS.

Andrew