Problems with unit selling/buying

[moRIs]

I have a mercenary camp that sells ogres. But i want that if a player doesn't have the "ogre" upgrade researched to not be able to buy ogres from the mercenary camp (same as knights can't be trained if a castle is not upgraded for example).
I tried adding the "ogre" research to the Techtree - Requirements in the ogre unit panel but that only works if the unit is trained, not sold.
How to do this?

 

[TimeDead]

Make a trigger that checks the research tech of the player. And then allows it to be sold?

 

[moRIs]

Ok, but how does it allow or prevent the unit to be sold?

 

[TimeDead]

Um. Thats what I am trying to think of. Go make a trigger, and use in event "Player purchases" I think theirs one like that I am unsure I have a RoC World Editor. Because of the map im making.

 

[moRIs]

I can remove the unit from the game (is the buying player doesn't have the research), but what about the gold he spent? There's gotta be an easier way.

 

[TimeDead]

Just add to the trigger

• Player - Add X to (Triggering player) Current gold

After you remove the unit?