Monitoring netlogon service

Hi

I am using nagios to monitor the netlogon service of a couple of my domain controllers, however have an issue whereby often the netlogon service will become paused due to a problem and not accept logon requests however nagios never reports this as an issue, the reason it doe snot report as an issue is the netlogon port is still active, does anyone know a way around this so we can monitor if the service state has changed rather than monitoring if port is up or not

your help greatly appreciated