[NL] **SoloGigabit** C2Q Q9300(1333Mhz)/8GB/6TB/1Gbit/7000GB €384/m The Netherlands

What script(s) could I use to keep a running total of bandwidth usage (month by month or just cumulative)? I can get stats since the server was last rebooted, and I have MRTG installed, but how do I tally numbers and calculate an actual bandwidth usage?

Thanks

James