VBA Secondary Axis - Line Chart

Hi, I wonder whether someone may be able to help me please.

Using a link I found here:
http://http://www.mrexcel.com/forum/excel-questions/485714-creating-chart-dynamic-range-size-visual-basic-applications.html I've put together the following code which creates a chart from a dynamic range.

Sub Test()

    Dim LastRow As Long
    Dim Rng1 As Range
    Dim ShName As String
    
    Sheets("All CDIO F'cst").Select
    
    With ActiveSheet
        LastRow = .Range("B" & .Rows.Count).End(xlUp).Row
        Set Rng1 = .Range("B9:N" & LastRow)
        ShName = .Name
    End With
    Charts.Add
    With ActiveChart
        .ChartType = xlColumnClustered
        .SetSourceData Source:=Rng1
        .Location Where:=xlLocationAsObject, Name:=ShName
    End With
End Sub

I am however a little unsure about how to progress this. I'd like to add a secondary axis as a line which appears on the chart ranging from "B8:N8 with B8 the Legend for the data series.

I just wondered whether someone may be able to look at this please and offer some guidance on how I may achieve this.

Many thanks and kind regards

Chris