How to restrict an unit?

[mhroczny1337]

Hello, I'm working on little modification - just to learn something and maybe start something bigger, I'm creating new unit (just scripts, not textures...), that summons another new unit; but i have a problem:
1. First unit need to be unique, I mean, it should not appear in enemy armies, or in shops other than I'll specify (it's already added to one place). I don't know how to do it.
2. Second unit should behave like summoned griffins - appear only in game, when summoned by first unit. I think that line
arenaonly=1
will do that, right?

(sorry for possible problems with my English)