Forcing Traffic to Proxy ?

Hi guys,

Not sure where else to post this but I could really do with some big brain power. Currently got a proxy server running. It works with both transparent and explicit proxy address.

Transparent works when you set the workstation gateway to the proxy server IP content gets filtered perfectly. However, I'd like to be able to force that network wide via pfSense if possible?

So far I've tried a rule similar to below. I've tried changing the Dest Address to WAN Net, WAN Address. Tried changing my NAT port for the proxy to the specified HTTP and HTTPS ports and I've tried the standard 80 and 443 port too. Just can't seem to get the traffic to go through the proxy.

LAN NAT Rule

Would greatly appreciate if anyone has any ideas?