Rewrite to same URL, different subdomain

In web.config I am rewriting an ugly url to /company/los-angelas like so:

<rewriteMaps><rewriteMap name="Friendly"><add key="/company/los-angeles" value="/content.asp?ID=IEH4VATYJI&amp;AID=8MH8X1DKHE" /></rewriteMap></rewriteMaps>

This works fine. Now I need to use the same pretty url to point to a new page on a subdomain, food.osas.com. Simply specifying the subdomain does not seem to work:

<rewriteMaps><rewriteMap name="Friendly"><add key="/company/los-angeles" value="/content.asp?ID=IEH4VATYJI&amp;AID=8MH8X1DKHE" /><add key="food.osas.com/company/los-angeles" value="/content.asp?ID=2NHGO78O55&amp;AID=F0HI6EGP5I" /></rewriteMap></rewriteMaps>

There are other rules set up (which I did not write nor do I understand), so let me know if you need to see more of the file.

Any suggestions on how to specify the same rewrite (key field) on a different subdomain?