URL redirect or rewrite

I have a situation where I need to detect a URL such as: http://www.domain.com/101 and automatically redirect to a different url that requests info from another server, such as: http://www.domain2.com/search?id=101 What would you guys suggest that would not interfere with other pages requests from the original server, such as: http://www.domain.com/page.html Note, changing the url is not an option. It must appear as the first example above. TIA cc