Try it in the sim.
Manually enter the speeds you want to be at by certain waypoints such as the next lowest flap maneuver speed as calculated by Vref plus 20,40,60, and 80. You might have a default of 240 below 10K but that can be modified to flaps up maneuver speed.On the VNAV descent page can enter a lower speed as appropriate for weight to be commanded below a certain altitude such as 210/3000. Perhaps enter flaps 5 speed at a stepdown fix and flaps 20 speed at the next fix(or flaps 10 speed as well if you have enough fixes. Then enter approach speed at the FAF.
Just prior to reaching the next waypoint with the next lower flap maneuver speed select the next greater flap setting.