SNMP Maximum call duration in seconds

Hi,

I want to monitor the maximum call duration with SNMP (MIB) on several Cisco 3640 routers with BRI (ISDN) interfaces. i've checked all existing Monitors but none offer what i need.

I also checked the Cisco site and found this CISCO MIB:
http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?objectInput=demandNbrMaxDuration&translate=Translate&submitValue=SUBMIT

This is what i need. If you reference the Cisco OID tree with the OpManger MIB browser im missing some MIB's from . iso (1) . org (3) . dod (6) . internet (1) . private (4) . enterprises (1) . cisco (9) .

I should have an ciscoMgmt (9) but in the OpManager MIB browser i only have products, local and temporary.

Can i import ther updated MIB from cisco (CISCO-ISDN-MIB)?

http://tools.cisco.com/Support/SNMP/do/BrowseMIB.do?local=en&step=2&mibName=CISCO-ISDN-MIB

Or is their a better way of monitoring maximum call duration on an Cisco 3640?

Thank you for you time.

Regards,
Andries