Has any of you run a FREE Refill Campaign, as a way to increase your business? If so, I appreciate any input, advice, etc. (inkjet only)

We are in our store 8 months now, and have been running a $5.00 off coupon in our local paper, with dismal response.

We are thinking:
-black cartridges only
-must have GOOD empty, or pay $3.00
-One per customer
-One week campaign
-Ad in paper, banner on storefront awning.

Thanks in advance for any feedback.
-K-