How do I make a KO shop?

How do I make a KO shop that relies the KO's from the ko/wo leaderboard?

-For example, imagine a gun costs 5 KO's, and I kill 5 people with a sword and I get my 5 kills to buy a gun. -But when I buy something with KO's the KO's dont decrease, they stay the same.

Sorry i dont know much about scripting

This Tutorial Should Help With Your KO Shop, Just Change The Values: http://wiki.roblox.com/index.php?title=Dialog_Shop_Tutorial