Want to NAT over VPN but not the gateway's own traffic

[Malcolm Matalka]

I'm trying to have the following setup:

I have a host that is acting as a WiFi access point and then NATing
traffic to the internet.  That host is running an OpenVPN client.  So
wlan0 traffic is NAT'd to tun0.  That is exactly what I want.  However,
I would like to keep this setup of the WiFi AP going through the VPN but
the traffic of the machine itself to go not go through the VPN.

Is this possible?  How?  I'm not sure what information I actually need
to get proper help.

/Malcolm