Time bomb not working

ROY UK kindly gave me a solution regarding expiry dates on an excel spread sheet using this coding, fantastic and works the only problem is,if the security setting on someone's machine is set to high the macro doesnt work and they can disable them so the time bomb does not work , i have set auto_run but this does not solve it

Private Sub Workbook_Open()
    'check if a start date exists
    If IsEmpty(Sheets("Hidden").Cells(1, 1)) Then
        'none exists so add today's date
        Sheets("Hidden").Cells(1, 1).Value = Date
        'if a start date has been recorded, check if it is less than 30 days from start
    ElseIf Date >= Sheets("Hidden").Cells(1, 1).Value + 2 Then
        'alert user that it has expired
        MsgBox "Trial period has expired ", vbOKOnly, "Trial Period Expired"
        'close the workbook without saving
        ThisWorkbook.Close (False)
    End If
End Sub