Fortigate 60C Load Balancing

Hi Fortinet experts

i installed a Fortigate 60C for load balancing purpose

so the use is to provide redundant internet using 2 internet providers

the internet providers both are not that great when it come to reliability:

the problems being:

1. when they upgrade their materials and that create a lot of connectivity issues

2. when too many users in the buillding are downloading their movies peak hours)

the options are limited,

and i have installed the 2 connections with the same weight

and the Fortigate provide 50/50 connectivity from both providers

The big question, is there a way that the Fortigate can switch to one provider only

when the other is obviously down

right now it seem that when one connection is having problem, the connecticity response time is terrible

because it still try to connect a down line

so it would be a 50/50 load balancing

that will turn to a 100/0 when one of the provider is down

thank you for any help

 and any suggestions are welcome

Hal