Popup message on file opening?

[JackTradeOne]

Is there a way to create a pop up message when a file is initially opened? Something like "Don't forget to check whatever"?

[#2]

Hi, It might be a better idea to put the warning in the text itself. A popup is VBA code, and chances are the user (or his security settings) prevent VBA execution. Kind regards Hans

[#3]

I understand. But assuming VBA execution is not a problem - how can it be done?
And even better - is there a way to do it without VBA? Using Script Lab or OfficeJs maybe?