Thanks for your efforts with the CSA marker for this officer.

The 45^th Mississippi Regiment formed in April 1862 from Hardcastle's Mississippi Battalion. The latter organized in late 1861 and fought at Shiloh. In July 1864 the 45th Mississippi reorganized as the 3rd Mississippi Battalion. History is available here --

http://www.rootsweb.com/~mscivilw/3rdbnmsinf.htm

Neither of these commands nor Captain Middleton had any connection to the 15^th Mississippi Regiment. Copies of Middleton's miiltary service file are available here.

Please feel free to reply if you have other questions.