I have a document that will need to be posted on a website available for
users to download & change/approve.

The approval process will not make any changes at all to the document.

However, I do need to know they've opened the document.

Is there a way to get the name/machine/ip or something regarding who
opens a file and when they open it?

If so, I would like to do something like that, and either write it to
something in the spreadsheet or as an audit trail in a database.

If there's no way to do this, I am considering writing a small app that
requires them to sign in (something I can record) to a website as a way
of determining when a user has seen a document.

Any help/advice appreciated.

BC