Kill Traffic if not using VPN service (Witopia, VikingVPN, etc)

[killscreenjon]

Good Morning Forum,
I need a little help.  I've searched through the forums and I couldn't find a close enough answer to what I'm looking for.  I'm using PF sense as a VPN that connects directly to a VPS already.  I have a firewall rule in place that forces all that traffic through that VPN tunnel.

However, my clients also use the Witopia client on their desktops as a secondary VPN.  I'd like have a firewall rule on PFsense that blocks any traffic that isn't using that Witopia connection.  Ideally, if someone tries to connect to the internet without using Witopia, they are redirected to a local webpage reminding them that their traffic is not secure and that they need to connect to Witopia first.

TL;DR: Would like some help creating firewall rules that allow only what is needed to establish and run a client vpn service like Witopia and deny all other traffic.  Thanks.