Originally Posted by Happy

You need to buy it at the hotel so the purchase is coded as a hotel charge (Travel). This is no different when people try to use AMEX offer of Spend X at Marriott, Get Y $ statement credit - only the charge directly comes from the property would work.

Call around your local Marriott properties to find which properties have gift cards on premises to sell. You would generally have better luck at Marriott, Renaissance and St. Regis, not so much with other brands.