conditional text strategy for Pro and Express versions

I'm using robohelp 9 and could use some help sorting out my conditional text strategy for a project.

* The project consists of a Pro and Express version

* The Pro version includes all the topics in the project

* The Express version includes a subset of topics from the Pro version

Since all untagged topics are included in a conditional text build, i wonder if i need to do the following:

* tag all topics as "Pro"

* add an additional tag to all express topics as "express"

My build expression will be "include express"

The problem i have with this solution is that i wonder if there is an simplier or easier solution than having to first tag all topics as "pro"

Is there a better way to solve this conditional build issue?