I have this issue where there is no way of knowing when a person is editing a page. This means one CMS user could unknowingly overwrite changes being worked on by another person by saving their own.

I need to create some kind of alert pop-up which says something like:

"This page is currently being edited by [CMS User]. Any changes you make and save will overwrite their changes."

I would have thought someone else has had this issue before or may be some existing package someone is aware of that can achieve this?