So, this works to add a series

Sub AddNewSeries()

    With ActiveChart.SeriesCollection.NewSeries
        .Name = ActiveSheet.Range("B5")
        .Values = ActiveSheet.Range("D5:D5")
        .XValues = ActiveSheet.Range("C5:C5")
    End With

End Sub
But I really need to reference the ranges as "Cells" so that I can put the values in a loop

For example, I want Range(Cells(4,5) , Cells(4,5)) instead of Range("D55"). But when I do this, I get an error.

Any idea how to make this work?