I have both Windows and Macs accessing files in my shared folder on my iCloud drive. We've had issues, on the windows side, with shared files before. Person A was in the file and made changes. While making those changes, person B opened the file to also make changes. Both saved their changes before closing the file. When we later opened the file only one of the updates took. I want to prevent that from happening again. So, my question is what happens when person A has the excel file open from iCloud and person B tries to access the same file while it is opened with person A?