Custom counter cache

class Category
has_many :tracks
end

class Track
belongs_to :category, :counter_cache => true

named_scope :converted, :conditions => {:converted => true}
named_scope :active, :conditions => {:active => true}
end

I want to make custom counters for scoped associations, e.g:

category.converted_tracks_count
category.active_tracks_count

And when track changes its converted, active, and category_id status
counters must be updated.

Any suggestions?