Dual Wan Help

hi there everyone, just want to ask if this is possible

1 Fiber Connection = 50mbps (WAN1)
1 4G/LTE Wireless Conncetion = 20-30mbps (WAN2)

The goal is when WAN1 is less than 30% speed, WAN2 will activate and do load balance with WAN1. And when WAN1 is stable again 60-70% speed, WAN2 will deactivate

is there a script or can it be done?

thanks a lot

rapnics sumbalat