settin gwuf with multiple vpns

Hello.
I want to combine two vpns. I want to make: host-> first vpn->second vpn-> internet. How should i have to configure the firewall, the guwf to allow TCP/UDP connections only trought the vpns? I want to be sure that every connection goes trough first vpn and then trough the second vpn, and there is no leaks. How should i configure the firewall? Thank you.