Timer with change in pc system

[alipba]

I'm not good at English
I want a timer code that is independent of the change in the date and time of the computer and lock the file after 30 days

 

[Yongle]

what triggers the countdown to start
- first time file is saved?
- something else?

 

[alipba]

what triggers the countdown to start
- first time file is saved?
- something else?

Opening the file will cause a countdown. But if the user changes the Windows date and time, it can not affect the file

 

[Yongle]

How do you propose not using the system clock might work?
It is the only clock there is!

Are you thinking of forcing the user to be connected to the Internet to use the file?
- that would allow the date and time to be verified

What type of file is it?
- an excel workbook?

 

[alipba]

Yes, Excel file.
I think if the user can use the clock and date of the system, then it can change the function of the code.
It is a good idea . If the user connects to the Internet once (once only) when using the file.