By Brandy McDonnellFeatures writerbmcdonnell@oklahoman.comOklahoma country music standout Blake Shelton and his pop icon girlfriend Gwen Stefani will be among the stars shining at Sunday's Grammy Awards.Shelton and Stefani, co-stars on the NBC show "The Voice," will perform their new duet, "Nobody But You," on the Grammys, airing live at 7 p.m.Read more on NewsOK.com