You don't need routing.  You need to remove the default gateway from
the VPN connection.  Go into the VPN connection's Properties |
Networking | Internet Protocol (TCP/IP) | Properties | Advanced.
Un-check "Use default gateway on remote network".

Two notes of caution:

1. Tell your office IT staff what you want to do and ask them whether
"split tunneling" (connecting  simultaneously to the VPN and to the
Internet on the same computer) is allowed.  Some companies forbid it
because of the security risk to the corporate network: your Internet
access would be outside the corporate firewall.

2. If the network that you VPN into has more than one subnet, you'll
need to define routes to other subnets after disabling the default
gateway on the VPN connection.