best sellers in top level category

[ScottShipley]

this ones a little hard to explain so i hope you can understand what i'm asking!

 

currently the best sellers box populates with all "best seller" if you're not within a category or if you are in a category it will populate from the current category and the child category below it if any. Thats great but if you have a category tree thats pretty deep then "best seller" doesn't work on the higher levels.

 

eg

home (shows best sellers from all products)

cat level 1 (shows no best sellers)

cat level 2 (shows no best sellers)

cat level 3 (shows best sellers from list below)

product list (shows best sellers from this list)

 

Is there an easy way to get best sellers to query the database for the best sellers from ALL subcategories (however deep they go) below the category you're in?