If you pulled the password out of the db and placed it in to $password_from_db and if your cookie was set as "password" then you can do this. (I too would never place the password as a cookie, for the users sake).
if($password == $password_from_db){
print "Cookies good. hmm";
}
if($password != $password_from_db){
print "What no cookie";
header("loaction:login.php");
}
This would have to be in the very start of you php doc becasue of the header code, you can remove it though. I use header codes to force the user in to area i want them.