Way to switch between DHCP and PPPoE?

On Mac OS 10.1 through 10.2.3, is there a way to Applscript the Network Control panel to switch between DHCP and PPPoE and back again? I can do this via Network Access Scripting in OS 9, but I’m not sure how to do that in OS X. It appears that one cannot get to the “Apply Now” activation sequence in OS X.