I have a form that lets visitors create a post. I want them to be able to choose what categories the post is in, but each post also needs to go into two additional categories. So have a Post Category field where people can check boxes for the category they want. I also have an admin-only field that should add the post to the two non-optional categories, but that field doesn't seem to be working - the post doesn't get saved in that category. I assume this is because I can't have two post category fields. So is there any way I can let users choose from a bunch of categories, but also force the post to have a few other categories?