Leeroy-

>What is the simpliest and most reliable method of detecting if a specific screen is already active in a given session to prevent mulitiple launches of a modeless screen?

No doubt 1/2 dozen of us are right now typing WEXIST() *g*, which should work well for you. I'll just note that while you're checking that, you can also make the one that's already open (if there is one) active, too. But you've probably already thought of this.