counter_cache through, is this possible?

Say I have A which has many B which has many C, ideally I want the
quickest way to get the count of C for A, a counter cache through an
association with B would do - but I don't think that exists. Any ideas?

No the counter_cache is on the belongs_to and if I try adding through
on the belongs to then it whinges, e.g. on C:

belongs_to :a, through => :b, :counter_cache => true

I get the error undefined local variable or method 'through'


What I've ended up doing is the following

class C < ActiveRecord::Base
    belongs_to :B

    after_create :increment_A_counter_cache
    after_destroy :decrement_A_counter_cache


    def increment_A_counter_cache
        A.increment_counter( 'c_count', )

    def decrement_A_counter_cache
        A.decrement_counter( 'c_count', )

It seems to work, I was just wondering if there was a way to do it
through the framework.