Series line not correct after split

[Schadenfreud]

I'm using this code to split a series line into 2 overlapping parts, so I can use different styles on them:

Sub backfillDataSeries()
    'make new series in Port Historical Risk
    'if there is a backfill date in Rolling window data
Dim cRange As Range
Dim i As Integer


For i = 3 To 122
    Set cRange = Sheet24.Cells(i, 4) 'Sheet 24 - Rolling_window_data
    If IsNumeric(cRange.Value) And Not IsEmpty(cRange.Value) And Not IsError(cRange.Value) Then 'iterate through range D3:D122
        With Sheet49.ChartObjects("Chart 4").Activate
            With ActiveChart.SeriesCollection(1) 'Sheet 49 - Port Historical Risk
                .Values = "=Rolling_window_data!$B$3:$B$" & i
                .XValues = "=Rolling_window_data!$A$3:$A$" & i
            End With
            With ActiveChart.SeriesCollection.NewSeries
                .Values = "=Rolling_window_data!$B$" & i & ":$B$122"
                .XValues = "=Rolling_window_data!$A$" & i & ":$A$122"
                .Name = "Backfilled"
                .Format.Line.DashStyle = msoLineDash
                
            End With
        End With
        Exit For
    End If
Next i
End Sub

This is how the line looks before I run the code:

And this is how it looks afterwards:

I think it prints mirrored. Can I get a mirror image of the 2nd line?

 

[Schadenfreud]

I figured out why it's mirrored - it was because it should be on the secondary Axis and it was on the primary one, but now both lines start from the left-most part of the chart, which shouldn't be the case.

 

[Schadenfreud]

After a tough battle I achieved the desired effect. Turns out you have to have 2 data columns, both with some blank values, to achieve the desired overlap effect.

Sub backfillDataSeries()
    'make new series in Port Historical Risk
    'if there is a backfill date in Rolling_window_data
Dim cellHasValue, backfilledData As Range
Dim backfillDate As Integer


For backfillDate = 3 To 122
    Set cellHasValue = Sheet24.Cells(backfillDate, 4) 'Sheet 24 - Rolling_window_data
    If IsNumeric(cellHasValue.Value) And Not IsEmpty(cellHasValue.Value) _
        And Not IsError(cellHasValue.Value) Then 'iterate through range D3:D122 to check for backfilled date
        With Sheet24
            Set backfilledData = .Range("B3", "B" & backfillDate)
            .Range("T3", "T" & backfillDate).Value = backfilledData
            .Range("B3", "B" & backfillDate - 1).ClearContents
        End With
        With Sheet49.ChartObjects("Chart 4").Activate 'Sheet 49 - Port Historical Risk
            With ActiveChart.SeriesCollection.NewSeries
                .Name = "=Rolling_window_data!$T$2"
                .Format.Line.DashStyle = msoLineDash
                .AxisGroup = xlSecondary
                .XValues = "=Rolling_window_data!$A$3:$A$122"
                .Values = "=Rolling_window_data!$T$3:$T$122"
            End With
        End With
        Exit For
    End If
Next backfillDate
End Sub