How can I toggle between DHCP and PPTP WAN using SES/AOSS button (WPS)

I'd like to conveniently switch between my 'native' DHCP ISP WAN connection and the PPTP VPN One, using the WPS (= SES/AOSS Button) button of my WNR3500L.

I sometimes have to cut PPTP, for some online kid's games. As I desactivated wireless access to GUI (to protect my router from my kids...) I have to turn on my main computer just for that..

Has someone an example of custom script that can be used to make this trhough Administration>Buttons/LED menu ?