By far your best bet is to hire a researcher.
A link is attached below. This guy has helped me in the past and charges just a bit more than the archives. In addition, if your soldier was a Confederate, this guy has more access to CSA material than the archives.
In general, these people do business all the time in record repositories. My colleague knows the people there and turns around your information far faster than the archives.
Good luck in your search,
James B. Ronan II
To Join the Company of Military Historians click here