Help me to Load Balancing betwen 3 LANS and 2 gateways

Could you help me how to do Load Balancing over two gateways but I have 3 diferents LAN´s in my MT ( 3 diferents interfaces ). Total interfaces = 05 ( 02 gateway + 03 Lans ).

you can see this topic

http://wiki.mikrotik.com/wiki/Load_Balancing_over_Multiple_Gateways