What you describe does not sound like the ideal use of what FileMaker can do. Copy and pasting data, for example, can be done with other methods that leave the clipboard intact so that such a script does not mysteriously change data that the user may have previously copied.
But to answer your question, if you were to rename either file or relocated it to a different place relative to the other file, your script will break. To fix it, Open Manage | External Data sources in the file that you aren't renaming and update the external data source reference to refer to the new file by it's new name.
Thanks so much. I understand about not making ideal use of FMP, but, for now, I'm stuck with what I have.
I'll give your suggestion a try.
Yet there are very simple changes that will still produce thees results without any need for copy and paste.
The simplest is to pass the data to the second file's script in a script parameter.