Nah, it works off the item placed upon itThats the ones :D
Can you make one that works by event?
Like-
OnActivate==>Self==>Buyweapon[Price][Name of weapon(drop down menu)]
OnActivate==>Self==>Sellweapon[price]
OnActivate==>Self==>Rankweapon[Price][Name of weapon(drop down menu)]
Rank weapon is kinda how you said in OP, buy weapon, never have to buy again.
It works just like your thing, but could you add it where there's an RTB pref on whether to not show a popup or to show one?