dual wan setup with wan2 taking over once wan1 has hit 8mb download threshhold

Good Day Mikrotik Engineers

Please would someone with more brain than me guide me down the right path(there must be many of you)

I am attempting to setup my mikrotik with two wan ports as a sort of load balancing setup. However i only want the second port to start routing once my first port is using more than 8mb download.
Is this possible
i imagine i would need to set some queue tree and mangle rules in place but im not sure on what path to take.

Any direction or assistance would be much appreciated.

Bandwidth-based load-balancing with failover. The easy way.
https://mum.mikrotik.com/presentations/US12/tomas.pdf