Cookie detecting and redirecting script wanted

I have built a website for my brother that requires visitors to "Accept" the terms and conditions (one time only) before entry to the site is allowed. However, people can still access the site without having to "Accept" these terms if they happen to be sent a url from a friend that does not direct them straight to the index.html file.

I am looking for a cookie script that will check for this required cookie on EVERY page of the site and when it fails to locate it visitors are directed to the index.html file where they will be required to accept the terms and conditions first.

I am also wondering if there is a possibility that I can alter the current cookie script to do this and then just paste it into all pages in the site.

Here's the current script below...... it was written by someone else and so I've kept their information intact. Also on the following webpage they have stated that altering or modifying this script is permitted.

http://javascript.internet.com/cookies/cookie-redirect.html

<script language="javascript" type="text/javascript">

2) ? argv[2] : null;
var path = (argc > 3) ? argv[3] : null;
var domain = (argc > 4) ? argv[4] : null;
var secure = (argc > 5) ? argv[5] : false;
document.cookie = name + "=" + escape (value) +
((expires == null) ? "" : ("; expires=" + expires.toGMTString())) +
((path == null) ? "" : ("; path=" + path)) +
((domain == null) ? "" : ("; domain=" + domain)) +
((secure == true) ? "; secure" : "");
}
function DeleteCookie (name) {
var exp = new Date();
exp.setTime (exp.getTime() - 1);
var cval = GetCookie (name);
document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString();
}

var favorite = GetCookie('yes');

if (favorite != null) {
switch (favorite) {
case 'yes' : url = 'homepage.html'; // change these!
break;
}
window.location.href = url;
}
// End -->
</script>

Any help or advice would be very much appreciated. Thanks in advance.