How do i rewrite/redirect urls?

[kripz]

A web application i use constantly downloads stuff from the web. I've got squid3 in transparent mode.

It's URLs are something like http://server1.domain.com/file.exe, http://server2.domain.com/file.exe.

I would like to force everything to server1, if possible fall back to server2 if the file does not exist (but that's not important for now).

How can i achieve this?