このほうが汎用的なのかな
Set obj = Application.InputBox("2列選択", Type:=8)
Set obj1 = Application.Range(obj.Cells(1, 1), obj.Cells(obj.Count / 2, 1))
Set obj2 = Application.Range(obj.Cells(1, 2), obj.Cells(obj.Count / 2, 2))