Sub Macro1()
'assuming all cells are contiguous
Dim Rws As Integer
Columns("A:A").Insert Shift:=xlToRight
[a1] = "SortNo"
Rws = [a1].CurrentRegion.Rows.Count
[a2] = 1
Range(Cells(2, 1), Cells(Rws, 1)).DataSeries
End Sub