Unit Pricing Trigger

Unit Pricing Trigger

Does anyone know how to make a unit cost more every time you purchase it? I was searching through the editor and I was unable to find a trigger that would perform such a function. Perhaps I should use JASS?
Thanks in advance

Unit cost = constant integer value

you CAN"T change it.

you only may make a "dialog buying" or a "chat buying"

Of course you may have an ability with levels,next level will need to have more money.

Okay, here's how I'd do it:
You've got an interger variable for the additional price of the unit, and the building which sells them.

Event: Building sells a unit
If: player gold < [aditional price]
Then: Remove [Unit sold], display message to player(Buyer of unit): "Bugger off, don't you don't have enougth gold"
Else: Take additional price gold away from buyer Set additional price=additional price + 100


That should work. Can't check now, if doesn't work, or you need help, just ask.