query_posts query_string category__not_in

I’m trying to use that new taxonomy for query_posts so my index.php can do some fancy stuff.

I want to use “category__not_in” in my query_posts, but am unsure of how to fit $query_string in the whole statement. The only example I’ve seen is the one in the codex, where it mentions at the very bottom:
query_posts(array(‘category__and’=>array(1,3),’showposts’=>2,’orderby’=>title,’order’=>DESC));

Indicating an array can be passed to query_posts. But how do I fit $query_string in there properly? THANKS!