Replacing items in shops with random items as they are bought

[Epix]

I'm trying to make a shop that starts with an inventory of randomly chosen items from a huge list, but for this example they'll be items A through K (11 items total). When, let's say item C, is bought by a player, I want item L (randomly chosen from the list of items not yet used in the shop) to replace it on the list, and item C to be deleted from the shop's inventory (until the total amount of items available in the shop is less than 11, at which point the old items would be recylced into the inventory).

So to summarize, I want bought items to be replaced by other random items as they are bought, so no two players can have the same item at the beginning of the game.

I have absolutely no idea of how to go about doing this, so any help would be greatly appreciated.

 

[DM Cross]

It's trigger related. I'm not 100% sure, but this is what I think would work.

E: A unit buys an item
C: Item bought is equal to <your item>
A: Replace <your item> with <your other item>

Now, if you want this to be RANDOM, you'll have to, obviously, use a random integer. Save each item to a variable array, and randomly pick from the array

Hope that helps some.