Okay...if I were you, I'd have an auto incrementing primary key.
Now, depending on how exactly you want the new news number to work, you could, each time the client views a page, update the cookie with the highest news primary key. Then, the next time they view a page, compare the value stored in the cookie with the current primary key: "SELECT count(*) AS numNew FROM Table WHERE primaryKey > $cookievalue"
Hope this helps....
-Rich