if sapped, if feared, if disoriented, if sheeped, THEN use the trinket. Otherwise dont.
I had a proper go at this some time ago. Maybe over a year, in fact. You can step through your player's debuffs and look for specific debuffs by either name or texture and conditionally trigger your trinket.

That works perfectly.

Until you're in combat, then one of the functions (I don't remember which) becomes private and the macro craps out with an error message!

edit:
Managed to find the original thread from when I had a go at this.