bandwidth usage

[Aaron Collins]

I'm going to attempt to add the ablity to do bandwidth utilization 
charges in fresside based on the 95 percentile. And charge for over 
usage, can you recomend a good starting point?  I'm reading through the 
docs & mail archives and I notice several people have started this great 
hunt.  I plan on using MRTG with the 95.pl script from sean adams to 
create the averages. Then I'll throw those into a sql db.  What I'm 
wondering is, is their a way to add a hook into freeside so that at the 
end of the billing period, it will run a custom script that I write and 
pass it a value like a (username || userid) and be able to add the 
returned value on to the overall monthly bill?  
  If you feel that I'm aproaching this wrong, could you offer a better 
solution?