there are two things you can do: the first thing is logging the ip-adress in the db and every time this page is called you can compare if this ip-adress is in the db or not. if it is you won't count. otherwise you can use your counter ...
the second choise is, like you said, setting a cookie. (http://www.php.net/manual/en/function.setcookie.php)
and then after setting the cookie you can look if the cookie with its special content is set or not. e.g name the cookie count and thge value true. then:
if($count == "true") {
//count
}else{
//don't
}
maybe you got a idea
ali