Vending Machine Script Help

I'm working on making a vending machine that uses back/next button prims to control a central display prim. I've successfully rigged the buttons to control the display based on a notecard's info (changes display prim's texture, sets correct values for name and price, etc) but now I'm at the step to actually apply the price so a user gets the payment dialog and I'm not sure of how to get this to work.

I've used:

llSetPayPrice (PAY_HIDE, [itemPrice, PAY_HIDE, PAY_HIDE, PAY_HIDE]);

after setting itemPrice but I think that the linking is making this behave incorrectly (pay option is on the right-click wheel, but greyed out.)

The display prim is the last in the link chain and the main vending script is located in this prim.

I'm trying to set the vendor up so that when a customer finds an item they want to buy, they'll right-click to pay, and then the vendor will supply the item from it's inventory.

Any ideas (I'm assuming I'm missing something I'll eventually kick myself for it being 'obvious'.)

From the Scripting Wiki: "This function [llSetPayPrice] has no effect if the state that it's used in does not implement a money event handler."

Oops! Thanks