Excel and SharePoint Permissions

[BrettOlbrys1]

I have an Excel file that I share with 100+ people on a SharePoint site. I create personal backup copies of the original file any time I make a change, but when I was having someone share their screen with me because of a file issue, the person had the ability to SAVE the file back to SharePoint and overwrite the original file, which I do not want people to be able to do.

How do I configure the Excel file on a SharePoint site so that if they open the file in the desktop app (Excel), they CAN'T overwrite the original file or save a copy on that SharePoint site at all?

Thanks

Brett