one solution would be to buy "netqos" netflow accounting software - but
it isnt really cheap :)
if you want to go for any open source solutions,
i would suggst to look after "flowd" and some custom
perl scripts / database. perhabs any consultans can
deliver a customised version for your business.
netflow doesnt have to be licensed additional, it is
a build-in function for ios.
bye,
-- randy