RB 750 GL (1 ISP + 1ISP = DOUBLE SPEED) NEW USER PLEASE HELP

I have just purchased the Routerboard 750GL. I want to add two dynamic isp ip and merge the speed of two isp connection for the getting maximum speed. I am a new user of Mikrotek. Please someone help me. For exp one isp 2mb + 2 mb isp = 4 mb. and one thing more if my one isp is failed then all the load would be shifted on other isp automatically. Please pleas help me.

Double post:

http://forum.mikrotik.com/t/routerboard-750-gl/60849/1