How to call directly a unit in a tag expression

Hello, I am working on an army builder version for TOW. I have achieved to get some stuff working but I have long way yet.

Anyway, I now stuck in a detail I would like to ask for your help. I have created a list of magic armours the characters would be able to apply for (all gathered in an "option" and attached to each character by a "Linkset"). But of course, some of the character will not be able to select a magic armour, so for that my aim is to put inside this "Magic Armour List " option, in LIVE section, the name of the units I want to exclude from applying to magi armour. Here is where I get stuck. I would like to use the name of the unit directly to exclude:

!unitid.Assasin

But this doesn’t work, it says: "Tag 'unitid.Assasin ' not defined"

Anyone know how I can correctly write this expression?
I have been able to get it working creating a new tag group (an a tag) and giving this tag to the unit. But I would like to simplify the process.

I realize it's been months since you asked this, so you've probably figured it out by now, but anyway:

The way I would do it is to add a tag to the units (or to linksets attached to the units, or ...) that specify that this unit can (or cannot) take that kind of armor.

Both units and the items should of course have that tag visible to them.

This is a cleaner model than making units depend on items and items depend on units.

Thank You so much for the aswer, yes i solved some how. Anyway apreciated the answer