Hi Etienne,
In your case, I would like to suggest you unlock ranges on a protected worksheet for users to edit. You can select the cell, click Review>Allow Edit Ranges>New, you can enter different passwords for
every user (e.g. their username) or click Permissions to select the user in your domain. After that, you should protect the sheet. You can upload the file to cloud like SharePoint team site, the users will enter their password when they want to edit the cell.
(Note: please choose Open in Excel, this function is not available in Excel Online.)
For the detailed steps, please refer to the
Unlock ranges on a protected worksheet for users to edit part
in the following article:
Lock or unlock specific areas of a protected
worksheet
Although it is a little complex that you need to create the range for each user, it can achieve your goal. You may also monitor this thread to see if other community members have more easy solution.
Regards,
Zixuan