Client Specific Promo Code for employee gifts

[MikeSmoresGuy]

I have a client that hosts webinars.  They would like me to have a promo code that every webinar attendee can receive.  The promo code needs to allow for the item to be free to the webinar attendee as well as free shipping. No cost to the attendee of the webinar.  I would then count how many promo codes were used in a month and invoice the client.

For example: Mary attends webinar. She gets the Promo Code FREEKIT. Goes to my website, "buys" a s'mores kit using FREEKIT. No cost to her. No shipping fee.  Then I invoice my client at the end of the month for how many FREEKIT promo codes were used.