Squid Proxy - How to route squid traffic via different outbound interface?

[foss-johnny]

I've got a squid forwarding proxy running on my LAN interface (gateway IP) on default port 3128.

What firewall/NAT rule settings must be configured to route squids outbound traffic via a different WAN interface?

For example:

1. Can I create a firewall rule that filters traffic sent to the squid destination service port 3128, and then NAT that to a different WAN interface default gateway?

Or

2. Run squid proxy on a LAN sub-interface (Unique IP), and then create a firewall rule that specifies that any traffic originating from the sub-interface address routes via different WAN inteface gateway?

Cheers!