FortiGate 6.0.3 Route Monitoring

I have Fortigate 501E which route to 90 Branch offices via 2 ISP links. I prefer ISP A as a primary and other as secondary. I configured ISP A with AD 10 and ISP B AD 20. I would like to monitor the static route to each branch offices if the primary link down the route will go through the secondary. On FortiGate I would an option is Link-Monitoring which monitor the interface and will update all of routes of monitored interface. It's what we don't want. We want the Fortigate to remove the specific route only not all the routes of the interface.

Anybody have experienced with that?