problem PPTP VPN client mode connection

Hi
i’ve a mikrotik rb750 and use this for connect to vpn service. i’ve configured be described in this link:

https://support.purevpn.com/mikrotik-configuration

but have a big problem.
if my clientpptp connection drop, all lan connection are redirect to standard gateway. i want stop all lan routed connection if pptp connection dropped.
thnx in advance