How to add 2 static IP and 1 PPPoE WAN connection in RB1200? Loadbalancing between 3 WAN Connection

How to add 2 static IP and 1 PPPoE WAN connection in RB1200? I have 2 static IP and running fine but now I want an extra PPPoE Connection. How to setup an extra connection without making network down? I also want to do Load balancing in these 3 WAN link. Any suggestions?