Sorting subfolders

[wozza]

EDIT: Realised I could just add numbers to the "Sort Title" of each video (HP 1, HP 2 etc)

Is there a way I change the sort order of subfolders on a folder-by-folder basis? E.g. I have the following structure:

Library
> Action & Adventure
>> Harry Potter
>>>Harry Potters and the Philospher's Stone
>>>Harry Potter and the Chamber of Secrets
...etc

My problem is that the "Action & Adventure" root folder is sorted by Sort Title (Ascending) so that it's easy to browse, but I'd like the HP subfolder (and other subfolders for some of my other movie series) sorted by release date. All the HP subfolder properties are greyed out, so I can't change anything there.

BTW the structure of the database reflects the folder structure - I haven't created any fancy playlists or anything, just imported my entire videos folder.

Thanks!