Hi there, I am selling DVDs on ebay. And I want to set up a promotion like this: If someone buys more than one DVDs from me, this guy can get $2 refund out of each extra DVD. For example, if buying 2 DVDs, then get $2 refund; if 3, then $4 refund. I feel my expression for such a promotion reads awkward. Can you advise a concise and normal one? Thx.