[mrtg] Calculate bandwidth transfered?

[Evan Platt]

This may be somewhat o/t, but hope someone here can help... I'm 
looking to somehow calculate bandwidth transferred. Would like to be 
able to see ok, last month, I downnloaded <X> megabytes, uploaded <x> 
megabytes...  Or even daily, weekly, etc...

Is there any tool that does this? Integrate with mrtg or using SNMP?

Thanks.

Oh, server is a os/x box, client is Windows XP Pro.

Evan