US redirect traffic script.

I need a script, that checks where you're from and from where you're referered from. So if your are from US AND your referer from [login to view URL]* even if its [login to view URL] Your going to be redirected to another website for example www.c.com. But if your from any other country and refered [login to view URL]* you will just go to the main site. So i want all the US traffic to be redirected to a site that i can choose and the rest goes to the main page.