I'm not sure how to do this. It seems simple though. I want to buy a deed, key and maybe a bill of sale at once. I don't know how to use dialogue, I've also considered having the merchant unlock a container after I buy the deed, or buy a box and when activated, is replaced with what I want.
So if you know how, please could you let me know how I can do this. Thanks

If the deed is a leter/book then from it's onRead event call box.activate(player), use disable/enablePlayerControls to close the inventory and the letter to imediatly display the box. Check my House Inventory Book if you wish as I do exactly that.