Custom query: multiple categories sorted differently

I run a website using MimboPro at http://www.mayatanfoundation.org.

I know that I can query posts from a certain category, i.e.:
query_posts(‘showposts=4&cat=33&orderby=rand’);

However, what if I want to query posts in a way that would combine different results from different categories in the following way:

1. Display X number of posts from category “News” in chronological order
2. And display X number of posts from category “Featured” in random order
3. “Featured” and “News” would have ideally be alternated, so that a random feature from any date would alternate with a news item in chronological order.