Workbook_activate - why doesn't it work

I put this in the "Workbook":

Private Sub workbook_activate()
alertTime = Now + TimeValue("00:00:10") 'delay for open indtil execute macro
closingTime = Now + TimeValue("00:00:15") 'delay fra open til close
Application.OnTime alertTime, "EventMacro"

If TimeSerial(6, 0, 0) < Now And TimeSerial(8, 0, 0) > Now Then
Application.OnTime closingTime, "CloseMacro"
End If
End Sub

Private Sub EventMacro()
Range("a500000").End(xlUp).Select

End Sub

Private Sub CloseMacro()
With ThisWorkbook
.Save
.Close
End With
End Sub

-- But is says that "EventMacro" cannot run? Can anyone help me out?