How to build an installer that takes advantage where it was downloaded from?

We have a web service product that includes a client-side utility developed in .NET. The services are deployed to several mirror sites around the globe and we have a landing page at each mirror allowing the user to download this utility. We want the installer (msi) for the client to communicate with the services at the same location where it was downloaded from. We have considered making this a user input or having a custom build for each mirror site but I would prefer to not include the service URLs in the installer and instead make the installer smart enough to configure the client URLs based on the site where the installer was downloaded from. Any suggestions?