Chart range auto refresh in excel vba

Private Sub Worksheet_activate()
 Dim wS As Worksheet, LastRow As Long
    Set wS = ThisWorkbook.Worksheets("Sheet1")    
    'Here we look in Column F
    LastRow = wS.Cells(wS.Rows.Count, "F").End(xlUp).Row
'LastRow = 5
'    MsgBox (LastRow)
 Dim cht As Chart
    Dim ser As Series
    Dim iSrs As Long, nSrs As Long
    Set cht = ActiveSheet.ChartObjects("Chart 1").Chart
    cht.SetSourceData Source:=Range("F1:" & "S" & LastRow)
End Sub