I found an arcaine way in the archives to solve my problem.
It was posted by John Morina from Pueblo systems in the year 2007.
In the loop where I import the data I add a command that changes the name of the file on disk to some generic name like "importfile.xlsx".
I then import the Excel data using "importfile.xlsx" in a fixed import script step
I then rename the file to it's original name before repeating the process with the next file.
This does of course require a plugin, but at least it provides a dynamic way to import the Excel data into FM.
What makes me wonder though is the fact that this flaw / limitation in Filemaker has been around since before 2007.
Which I feel is pretty amazing in it self.
I therefore wonder what it might take to get FMI to fix some of the older code in FM before adding more features?
In addition to the above I do of course need to add a test for .xls versus .xlsx before importing the data.
How do I mark this subject as closed?