How to construct these rewrite rules?

Hi,

I'm running Apache 2 on Linux. I was wondering if it is possible to
use mod_rewrite with an .htaccess file to achieve the following. I
have two domains, -- www.mydomain1.com and www.mydomain2.com, both
pointing to the same IP. What I want is that if someone types in
www.mydomain2.com, the URL is rewritten as www.mydomain2.com/index2.php.
However, if someone types in www.mydomain1.com/whatever, the URL is
rewritten as www.mydomain2.com/whatever.

Your help is greatly appreciated, - Dave