URL redirect

[Me]

I want to know if it is possible to mask a URL using mod_rewrite.

What i want is, if the url www.mysite.com is entered in a browser, the pages in the site www.notmysite.com should be displayed, but the URL in the address bar should not change. It should remail www.mysite.com.

I do this with frames now. But i want to know if this can be done with mod_rewrite.
If so, please provide the code.