How to check how many shared file users have the file open?

I have a Google Sheets file shared with a dozen editors. There's a relatively complex form that can't be run in Forms. I want to ensure in case multiple people have the file open that they don't overwrite each others' form entries.

Can I trap if more than one person has the file open? (I could then, for example, disable editing until the first user leaves the file.)

Education counts, but I'd like to avoid asking them to look top-right to see if others have the file open.

Thanks!

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