Select network card for Nagios

Hi everyone,
I’d like to know if is possible in a server running fedora 7 (yes, it’s time to upgrade :wink: ) with two network cards, each one pointing to a different network, and Nagios 3.0.6, to select for Nagios (and only for it) a specific network card to use (for example, if I don’t want to use eth0 but eth1) for his cheks, and how to do it.
Thank you for your patience and support.