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?