Originally Posted by thermopyle
Then when you run my program, whatever tag value you have in Custom_Field will be used to create the collection, and any books with that particular tag value will be added to it.
At least, this should work. I haven't done it myself (I don't use any tags other than author, title, and series), but as long as you have Calibre output the file with the tag as the path, my program can use the directories it creates accordingly.
Ah, interesting. If a tag creates a directory structure, does that mean if a book have, say, three tags assigned to it there will be three separate copies created on the Kindle?