Workbook_Open event do not working?

[beginner]

On this link I wrote about my problem and I attach my file *. Xlsm
When I save my Workbook as *. Xlsm in this case Workbook_Open event is functioning correctly.
If I save in the file format *. Xls, in this case on re-opening the file Workbook_Open event that does not work, nothing happens?

I tried to run the file in *. Xls format and after that nothing happens I've tried to run the following VBA code to check the event

Sub EnableEventsNow()
    Dim sMsg As String
    With Application
        sMsg = IIf(.EnableEvents, _
            "Events were already enabled.", _
            "Events are now enabled.")
        .EnableEvents = True
    End With
    MsgBox sMsg
End Sub

After activating this code (I put the cursor inside the VBA code) by pressing F5 on my keyboard, then I get the message "Events were allready enabled" means that the event has started?

Can someone help me and explain why it is not working Workbook_Open event in *. XLS file format

Improved thanks for any help.