Range(Cells(7, 1), Cells(7, 3)) = "一括入力"
Range(Range("A7"), Range("C7")) = "一括入力"
Range(Cells(7, 1), Range("C7")) = "一括入力"
Range(Range("A7"), Cells(7, 3)) = "一括入力"

結局セルの指定方法のひょうじゅんってどれなの?