You might look at the Buffalo Barracks website operated by Cliff Williams.If the army units in which you are interested were sent there at the close of the Second Seminole War in 1842, you will probably find your soldiers' names and other information in the "Muster Lists."The website is at http://www.buffalonet.org/army/http://www.buffalonet.org/army/
"Returns From Regular Army Infantry Regiments, June 1821-December 1916. M665. 300 rolls. DP."
"This microfilm publication reproduces the monthly returns that the AGO received from Regular Army infantry regiments from June 1821 to December 1916. The returns are arranged by regiment and thereunder chronologically."
These are remarkably complete records which include names, places, and events.Each regiment of infantry is listed separately and chronologically, so you can select the years you want to review.In the 2nd Infantry records, we found enlistment and discharge records for our ancestor.Soldiers on special duty are noted, so you might luck out and find the name of the person you are looking for, as we did.
These microfilms were not available at the NARA regional office near us, so we ordered them through the Family History Center of the LDS church and have kept them there on extended loan.