Transaction account builder: Populate Natural Account from project rule OR Category

Summary

I need to populate the natural account on a requistion first from project, or if no project, then from the category

Content

Hello, I'm having a problem with this.  I can do one, or the other, but I can't seem to get them working correctly together.  I'm certain I'm doing something simple, but incorrect.

The scenario is this:

When creating a requisition, Transaction Account Builder should first look to see if there's a project, if so, it should use the natural account derived from a mapping set created in Projects.  If not, it should derive the natural account from the procurement category.