Coupon created by Retail

[kooyii]

How can i let the customer created the coupon by themselves?

I mean:
1. Retail A come to my web site and created a Coupon Code
2. Retail A give the Code to their Client B
3. Client B come to my web site and buy product using the coupon code
4. Retail A earning money from the transaction

If anyone can let me know how to do it or are there any add-on/module to use? Thanks

[kooyii]

Are there any affiliate programme works like dreamhost?

that is:

1.People can generate their coupon code in our web site
2.They give the coupon to other people, and earning money from their client's transaction.

Any one knows where could find the module?