I don't know how many miles you need (and I don't have any DL miles), but this might be more appropriate in the Coupon Connection or the Delta forums -- they may be able to find ways to help you out.

When's your flight? How many miles do you need? Can you top your account off with a DL AMEX? If you 'do not use' an AMEX, don't understand why you can't start now..