Hello Jeff -
I dont think IP Accounting is supported for the PIX, But you could configure AAA Accounting using TACACS+ server syslog and RADIUS are not supported.
You could also try the following cmds to check connection info.
- show xlate detail
- show conn detail
The cmd for configuring AAA is aaa accounting
Pix(config)# aaa accounting include ¦ exclude accounting_service
Inbound ¦ outbound ¦ interface_name
Internal_IP_address internal_subnet_mask
External_IP_address external_subnet_mask
Group_tag
Pix(config)# aaa accounting match ACL_name
Inbound ¦ outbound ¦ interface_name group_tag
Hope this helps --