Ask about config squid proxy work on Wan

Sorry my bad English:

I have three wan interface name wan1,2,3. I want to create proxy on wan2,3. Then use the main wan is public address share to my friend for access to proxy with port 1000 for wan2 and 1001 for wan3 and also wan2 and 3 is pppoe connect and some time Ip changed. Please anyone know good solution to create a config for this please help me.