Sub aa()
Dim S As Worksheet
Dim CH As ChartObject
Dim R As Range
Dim i&
Dim A$
'---
Set S = ActiveSheet
For i& = 1 To 3
Set CH = S.ChartObjects(i&)
Select Case i&
Case 1
Set R = S.Range("$A$3:$A$" & S.[A3].End(xlDown).Row)
A$ = "=SERIES(,'" & S.Name & "'!" & R.Address & _
",'" & S.Name & "'!" & R.Offset(0, 1).Address & ",1)"
CH.Chart.SeriesCollection(1).Formula = A$
Case 2
Set R = S.Range("$C$3:$C$" & S.[C3].End(xlDown).Row)
A$ = "=SERIES(,,'" & S.Name & "'!" & R.Address & ",1)"
CH.Chart.SeriesCollection(1).Formula = A$
Case 3
Set R = S.Range("$A$3:$A$" & S.[A3].End(xlDown).Row)
A$ = "=SERIES(,,'" & S.Name & "'!" & R.Address & ",1)"
CH.Chart.SeriesCollection(1).Formula = A$
End Select
Next i&
[a1].Select
End Sub