Steve,

Only reliable method is to ping a know IP address outside your walls. See:

Re: Can I truly check for Internet connection? Thread #724735 Message #724761

>Does anyone know a surefire test to see if your PC/laptop/Handheld has a current IP connection? We have experimented with a few methods including using WinAPI methods and continue to get some false positives... i.e. creation of a flag file indicating a connection when none exists.
>
>I have searched back a ways and found nothing much.
>- Steve