I'm not sure if this is what you're looking for, but I had a similar problem when developing my 2d game builder and EFX animation editor. To get original file names of external BMAP files, I had to use text_for_dir :

You'll find a basic example in the manual. Just create a TEXT array for reading the strings. It will read the original names of all files within the selected folder and store it all into a TEXT array. Then you can just loop through the array and define/create/point to whatever is needed. I used this to read from a folder and create auto generated lists for external files in my EFX editor.