Discount Promo code generator

I will soon be selling a book through Amazon. As part of marketing, I would like to give my website visitors the option of entering the email addresses and names of five of their friends in order to get a discount code. After entering the addresses, a pre-written email addressed to their friends would be automatically sent, and a discount code would be emailed to the visitor.

Do you know of any WordPress plugins that would allow me to do this?