how to use something only once or limited times

[gameboy]

hey i m made a elves factions but i don't know how to do few things, like i want to make a power kinda thing which can used only once how do i do that?
and also how do in make a new way of gathering resources like building a building and then gathering the resource from there?
and how to make an resource exchange?

[@kukac@]

Well, the most usual solution is to make a new resource, and give only one of it to the player.

[gameboy]

no, i mean like putting a worker to work on the the building and by doing that getting additional resources

[verarticus]

try looking at the magic units energy thing maybe you could figure out something because im not sure how to eather