Help with a Pop up message

[JRad1988]

Hi all!

Seeking advice for creating a pop up message every time a specific document (that is already created) is opened.

Background - a document i have already created a certain amount of data into, to be used as a template document, but requires saving as a diff version first to avoid altering the template. A simple message of "please remember to save a copy first before altering"

Forgive my poor knowledge but this code for the message will need to go with document so it can be emailed around to various users.

Many thanks!