Time-of-day RADIUS accounting

Hi all, I wonder whether RADIUS can be easily extended to track the usage in every hour (or 30 mins) of the day? The current ACCT START/STOP and INTERIM UPDATE INTERVAL are per-session basis and hence it is hard to track the usage of each session in every hour. I can imagine that this would face some performance issue with many flows, but I think this feature will be very useful for time-dependent usage charging. It would be great if anyone gives me some insight on this. Thanks, DataWizApp Team