The simplest way that I can think of is to use DeltaServer to report the SMDR to file(s) on a drive.
Import the log files (which are comma-delimited CSV files) into Microsoft Access. You can then run a query with Totals turned on. Group by line or extension if you wish and be sure and select only external calls (i.e. direction = I and is_internal = 0 and continuation = 0).
I believe the continuation is for calls that are transferred which creates a second SMDR entry (which you don't want). Err... Or maybe you do?
In any case, there is a wealth of information available in the log files. Keep in mind, the current day SMDR is written to a different file and is cumulative for that day. Until, DeltaServer renames it to ...date.log
Also, DeltaServer is free (located on the Admin disk in CBC folder.
Hope this helps.