I don't see any reason you cannot as long as the selling price has been agreed upon by the bank; however, I am not a mortgage pro and would recommend that you consult with same for the most accurate information. (I am currently working on an FHA deal (not a short sale) wherein the buyer has managed to acquire $10k for closing costs!).
Try consulting with:
John Grigos, Superior Mortgage (in business for over 25 years) @ 732.859.8585; or
Leah Plattis, Wells Fargo, 917-657-1965
Love and Peace,
Francesca Patrizio, Realtor, ePro