Windows Firewall connection rule to force VPN

I have a requirement to set up a firewall rule, so that all access to the
internet is forced via a VPN connection, such that it goes via a managed
proxy.

I'm struggling to work of the settings for this!

Can someone point me in the right direction please?

To elaborate further:

A home PC with a broadband connection. Set up a firewall rule, so that all
networking establishes an IPSEC connection to a VPN server, after which all
HTTP and HTTPS traffic is directed via a proxy server on the network into
which the VPN connects. There must be no way to disconnect the VPN and gain
'direct' access to the internet.

Thanks in antici

Martin.