Excel Project: Read only notification: Who is editing so i can ask them to get out

Hi Ben Bylsma,

Thanks for your updates. From the screenshot you shared with us, I think I could misunderstand you situation: I thought you would like to co-authoring on a workbook in you project. However, it seems that you save a project file in a OneDrive that can be accessed by some users, you got the prompt if the project file is opened by multiply user.

As it is not feasible to use co-authoring on Project, as OneDrive tend to be a place for storage while SharePoint is a good place for Collaboration. With license for Project, we may sync a project to SharePoint site so that anyone has access to the site can see the task.

1. Open a project file(.mpp)
2. Go to File>Save As>sync with SharePoint, you may create a new SharePoint site or sync to a task list in an existing site. Information for Create and manage a project task list
3. Click save, and you will see the task list in the site. You may open the task list in Project and changes will sync to the list. For more information: Open a task list in Project or Excel.
4. You can control users’ permission for the list. For more information: Customize permissions for a SharePoint list or library

For more information, you may check the article: Sync with a SharePoint tasks list & Collaborate in Project.

Hope these can help.

Regards,

Clark