disabling dial-up?

[Chris Beamis]

This may be a stupid question, but...

Is there a convenient way to make it so that I can disable the modem 
from dialing out while I'm using the machine?

Sometimes I'll be working on something that has nothing to do with 
anything online, and I don't have
mail or a web browser going, and the machine decides that it just _has_ 
to be connected for some reason,
and it commences to dial up.  I would like to have some say over 
whether or not I'm dialed into the ISP!

Thanks,
Chris