Way to notify users when using PowerPoint docs that someone else is editing the doc when trying to save changes to it.

What is hosting the Intranet site? SharePoint? If it is then there's built in collaboration tools. If it's "just" a file server then the second and subsequent person to open the file should see a message saying it's already open and they can then choose to open read only and be notified when the file is available for writing. If you want "real" collaboration and some very cool tools in this respect, check this out (but it means using Office 365) :

https://support.office.com/en-us/article/collaborate-with-office-365-ac05a41e-0b49-4420-9ebc-190ee4e744f4

Yes the files are on a file server where our intranet lives.
So I guess they would see a message when trying to edit the doc that someone else has it open and when they other person finishes with the doc, they would get notified?
Also can this be done if the file is saved in OneDrive? Meaning the users could all have the file open and making changes and their changes would be update real time as they make them or is this not the case?

Thanks for your quick response