If you want to reference other files, you should use a less ambiguous way to refer to them. Like a relative path or full absolute path. The fact that that weakness is because of a half-baked feature like that actually makes me lose even more respect.

Edit: thanks for the info though, it does add some missing context.

Whichever one has the smallest relative path to the workbook using it? How does it find the workbook if it isn't open already?

So throw an error at runtime on that macro, most workbooks aren't the target of a macro