If you can force users to click a button when they open the app, you can apply this:
Set the value of that column to a new “normal/fixed” column so that value is set in stone, and do that only when the “normal” column’s value is not standalone.
You won’t have a count of users who are currently logged in, if that’s what you are asking for. Since I see you mention the sheet of logged in details, I think you’re not asking for that log again.