to monitor bandwidth on an ASA excluding certain traffic

[maryg]

Hi Guys
In the company i work , we need to monitor traffic on an ASA device.
The problem is that 2 of our clients are using the same bandwidth so in the graphs I need to be able to exclude a certain traffic. for example on a network 192.168.x.x I need to be able to exclude 192.168.3.0 and see the rest.
so that I could get separate graphs for each client and see if any of them is going over their bandwidth limit.

I need a free solution:
1-We tried doing this using Netflow and Ntop plugin, but the graphs are not that great because I need more detail on the graph to be able to bill a client using the graph.It does not seem like the graph is showing the right amount of traffic. Also I could not find a way to exclude part of the same network I'm on. Do you know any way to do this on Ntop?

2- We are running Cacti but again how to exclude a part of the traffic from a graph?

3- I installed MRTG yesterday , found an option for filtering interfaces which I don't think will solve my problem but I'm going to try it by tomorrow!

4- We tried flow viewer and tried installing flow-tools which was a waste of time because they don't suport Netflow version 9 which was designed for cisco ASAs.

I'll appreciate any suggestions for this problem.( It doesn't matter if it's through snmp or netflow.)