Detected by side - specific

[Nemanjic 71]

Successfully used this code for years when I want specific units to activate the trigger and similar stuff but:

How to do this for a specific unit only and not for the whole side so messanger1 (civilian) activates the trigger when detecting any opfor presented anywhere on the map?

Tried:

 

Have read everything but there are only examples for  "side present" activation type. I need "detected by specific unit"

Have also tried to set trigger owner to messanger but nothing happens.

 

Detailed: 

There is a village full of civilians and only if one of them (messanger1) see any opfor - then fire trigger

[Nemanjic 71]

I found knowsAbout