Configure VPN Connection Using Non-Standard Port

I need to configure my Mac to connect to a VPN server using PPTP over a port other than 1723.

I am hosting my own VPN server on my router (dd-wrt) using PPTP (Point to Point Tunneling Protocol). I also need to connect to the VPN at work using PPTP. Since they both use PPTP over port 1723, as soon as my outbound connection gets to the WAN interface of the router, the traffic is redirected to the router VPN server instead of being sent to the internet. To remedy this, I changed my port forwarding rule to accept VPN connections on 17231 and send that traffic to the VPN router.

The short story is that in order to connect to my home VPN, I need to specify which port to send the traffic on for that interface. I tried changing the VPN server address from "home.vpn.com" to "home.vpn.com:17321", but that did not work. Any help would be appreciated. Thanks in advance.