[1.7.2] Help with rightclick Item

[reindeer]

So i need help with rightclicking an item. I want so if you rightclick and item with another item in your inventory you get a new item. For example: Rightclicking with iron pickaxe with a diamond in your inventory will delete the pickaxe and the diamond and give you a diamond pickaxe

[reindeer]

Yes but i can't figure out how to remove both the diamond and the pickaxe