Adding a "Quantity Amount" to an Attribute

[TurtleDove]

I'm planning on selling an item either as a "single" (1 item) for $2.00 or as a "pair" (2 items) for $3.50. The customer has the ability to choose which one they want through a dropdown menu. How do I make it so that when the customer chooses the "pair" and purchases it, TWO items will be subtracted from the Quantity stock?

[Ajeh]

Have you looked at the Product Price Manager and the Discount Quantities ...