Front-end, Back-end and htaccess

[eluser]Sceneshift[/eluser]
I've done a fair amount of searching and I can't seem to find a solution to this problem.

I have the following file structure:

Code:

application
- admin
- site
system

And of course two php files (index.php and admin.php) both located in the root. The site is working fine, but I am trying to configure my htaccess file so that anything http://www.mysite.com/admin/ will read the admin.php file and ANYTHING ELSE will read the index.php file.

Can anyone help?