Monitoring Backup ISDN lines using Oreon

Hi,

My company recently implemented the Oreon front end for Nagios. The problem I am having is monitoring ACTIVE ISDN calls if the main ADSL line was to go down on a router. Can any one help me on how to configure this in Oreon or is it not possible and I have to change the nagios config files directly?

Cheers for any input.

Jimmy