apache 2.2 - mod_rewrite query about cross domains on same server

I've only ever used mod_rewrite to do friendly URLs, but have a query from a client. They want a page inside a site, to be associated with a domain www.domain2.com.

The site sits on www.domain1.com. He wants the following page for example www.domain1.com/thispage/ to be accessed using www.domain2.com. domain1 and domain2 point to the same server.

A simple redirect wont cut it, cause they want to hide the fact the page is under a different domain. I always thought doing mod-rewrites on domains was suicide when coming to maintainability/usability. Maybe im wrong.

Also frames are out of the question.

Thanks

--Mark