Maybe this will give you some ideas.
Sub Macro1()
Dim outstanding As Range
Dim backlog As Range
Set outstanding = Sheet1.Range(Cells(2, 1), Cells(11, 1))
Set backlog = Sheet1.Range(Cells(2, 2), Cells(11, 2))
ActiveSheet.ChartObjects("Chart 1").Activate
ActiveChart.ChartArea.Select
ActiveChart.SeriesCollection(1).Values = outstanding
ActiveChart.SeriesCollection(2).Values = backlog
End Sub
Sub Macro2()
Dim outstanding As Range
Dim backlog As Range
Range("A1").Select 'Make sure that no object is selected.
Set outstanding = ActiveSheet.Range("A2", Range("A" & Rows.Count).End(xlUp))
Set backlog = ActiveSheet.Range("B2", Range("B" & Rows.Count).End(xlUp))
ActiveSheet.ChartObjects("Chart 1").Activate
ActiveChart.SeriesCollection(1).Select
ActiveChart.SeriesCollection(1).Values = "=Sheet1!" & outstanding.Address(True, True, xlR1C1)
ActiveChart.SeriesCollection(2).Select
ActiveChart.SeriesCollection(2).Values = "=Sheet1!" & backlog.Address(True, True, xlR1C1)
Range("A1").Select
End Sub