Hi c7015, try adapting the following code into your procedure. Let me know if you need more assistance. 
Sub c7015()

    Dim Rng1 As Range, Rng2 As Range
    Dim Ws As Worksheet
    Dim DynamicRange As Range
    
    Set Ws = Worksheets("Sheet1")
    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    '''Set Rng1 & Rng2's locations and then add them via Union  '''
    '''to the DynamicRange variable.                            '''
    Set Rng1 = Ws.Range(Ws.Cells(20, 3), Ws.Cells(Ws.Rows.Count, 3).End(xlUp))
    Set Rng2 = Ws.Range(Ws.Cells(20, 5), Ws.Cells(Ws.Rows.Count, 8).End(xlUp))
    Set DynamicRange = Union(Rng1, Rng2)
    
    ActiveSheet.Shapes.AddChart.Select
    ActiveChart.ChartType = xlLine
    ActiveChart.SetSourceData Source:=DynamicRange
    
End Sub