I believe you are referring to the Battle of Somerville Heights, Oberations in the Shenandoah Valley, fought May 7, 1862.

As near as I can tell, the site is somewhat to the East of Winchester. There is a sign somewhere on Rt. 656 East of US 340.

A Goggle search, "Battle of Somerville Heights", will yield a number of hits.

Unfortunately, my CD Rom copy of the Official Records has packed up this evening. However, I did find two Federal reports which start on page 458, Vol. 15.

George Martin