Combine SNMP Data?

[Jake Pollmann]

Is is possible to combine stats from more than one source into one
graph?  For example, I'd like to sum the ifOutOctets from four
different routers to get the current total utilization of wan links. 
I didn't see anything obvious from the mailing list or a quick glance
at the source.

On a tangent, it would be even better if I could use the same graphs
to do 95% caclulations.  I don't believe the current data rentention
is appropriate for long term calculations that require precision.  How
easy would it be to use RRD's for the backend data?

Thanks,

Jake Pollmann
jpollmann at consonus.com