block ip leaks if vpn disconnects

Hello,
Ok, so as I rather prefer using the openvpn gui to those vpns exe's which may or may not have to be dangerous, I'd like to find a way to block internet in case one of the two disconnects, thus leaking the real IP.
I run the 1st vpn on host on win7 and the 2nd vpn NAT ed on the guest win xp sp3.
How can I achieve that given that I don't use windows firewall nor comodo firewall, I have Online Armor and I failed to find a good rule to block internet in case of a disconnection.

Can anyone help?

 

See this -https://xerobank.com/support/articles/how-to-prevent-vpn-dns-leaks/-

and this thread https://www.wilderssecurity.com/showthread.php?p=1872112

 

Thanks mirimir, that's what I needed!

 

http://www.guavi.com/vpncheck_pro.php

That's what I use.