Reporting outbound and inbound traffic?

Hello,

We have three locations and we need the ability to generate reports that show outbound and inbound bandwidth usage for our WAN and VPN connections.

I find the default reports too simplistic. Is there a way to generate these detailing actual bytes uploaded/downloaded on the different interfaces etc..? if not, then what other products are there?

I have tried setting up a firewall rule, to flag all outbound traffic, but this still does not record actual bandwidth usage, just sessions.

thanks