User access and statistics

[rgr]

I am sorry but my english not is very good. I am try to explain the problem.

I use MRTG to monitoring the Cisco routers. The problem is that I want to obtain more information than the graphic of the traffic in the interface because I have some PRI ISDN with a big number f users. I need to obtain statistics about:

How many time is a user connected?
How many users are connected at same time?
How many traffic produce a user?

I know some comands like: show user, show dialer, .. but I need to know is there are any program to obtain the statistics that I need.

Thanks in advance