Marketpress Coupons - need one use per person

Hi,

I want to give a coupon to welcome people who purchase something on our site for the first time, so when they come back and purchase something else they get , say, 15% off that purchase, but then they can't keep using the coupon over and over agian. It looks like I can either have everyone use that discount code as many times as they want, or just have one person use it once (which makes no sense).

How can I create a coupon that many people can use just once?

Thanks,

Sherry