post__not_in multiple criteria?

Hi folks,

I have a secondary query on my page that is currently set up as follows:

query_posts(array('post__not_in'=>$do_not_duplicate,'offset'=> 3));

Now I need to exclude an individual post from this loop. I tried using post__not_in a second time, and different variations for syntax to try and give it 2 definitions – not working. Is it possible? Or does anyone know of a different way to exclude an individual post ?

thanks!
-jennyb