Michael Sparling spent a recent afternoon helping an injured soldier around Walter Reed Army Medical Center. It was a gesture he has performed many times in the past year and a half since his son also arrived at the hospital to recover from war injuries received in Iraq, but one that may soon be coming to an end. "When my son leaves, I don't know if I'll be able to," said Mr. Sparling who also volunteers his time, expertise and energy to help other families navigate the paperwork and stress he has faced during his son's recovery.His son, Joshua, 25,...