Thanks. This worked for me.
If I were to make a suggestion, the menu for excluding categories is a little confusing. For example, why am I setting up the "Inclusion/Exclusion" then picking "Exclude from...? Why couldn't we just use the second "Exclude from..." area?
Also, is there a way to hide the category name itself from the category list that users see?
Anyway, thanks again. The main thing I needed was for the post not to show up on the main page, and it achieved that purpose.