I’m not sure if I got your idea …
The way to so some action before importing have to be the pmxi_before_xml_import hook and there by fidgeting with PHP-Code to filter the file, whose name and hereabout are to be extracted from some other templates or whatever WP All Import calls the setting of an import routine. I’m sorry, not my cup of tea.
But well, there is Filtering With XPath: In Step 2 of WP All Import, you can specify filtering options to only import records in your file that match your criteria. Perhaps this could be the solution. And why the heck didn’t I recognise this eature before?
To be on the save side I just wrote a minor script to filter an uploaded CSV-file on the server and save it with an unique file name.
