>>I came upon FileToStr() for situations like this because I needed a way to copy a file to a different directory, and Copy File was acting up on Excel sheets which were currently open, and FileToStr() and then StrToFile() was the solution.
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>>That's all I know :).
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>Yes, it depends on the associated program that opens the file. AFAIK, Excel creates the temporary file and actually does not work with the original file until you want to save it. But many other programs like FTP or DOS commands with redirected output to file, they do not allow to work with this file while in process of writing.

But Excel still wouldn't let me Copy File that it had open. So even if it works off a temp file, it still has a handle to the original - probably to signal to other users that it's open and to offer to open readonly.