I have never used Redbox before so I have no idea how this works but a friend of mine works for the company and told me:

"We received a Friends and Family Freebie discount code at work today. The promo code is only good for today (Friday November, 14th).
The code is: NOV14
You can use the code multiple times if you use different cards for each transaction."

I hope this works for ya.

Code: NOV10

The code is valid through 11/10 for Online Reservations use the code up to 5 times, each must be a separate transaction on the same card.