Hi Terry,
It's definitely possible. I think the manual may be incorrect, it mentions .ude files when I believe they need to be .udd (this was the case with PCM 2.0, maybe 2.1 uses the .ude extension now).
I've attached a sample configuration for a server, with a trigger to launch a remote desktop session.
After putting the files in the <PCM>/server/config/devconfig/extern directory, go to the Global:Discovery Status
window {Preferences->Discovery->Status] and click Rescan for user defined devices. You'll then need to restart PCM for any triggers to show up.
Hope this helps.
Matt
</PCM>