Setting Do set servo

I want to know if I can set a Do set servo command after the last waypoint?
I want my boat to goto a waypoint then actavate a servo type relay and turn off the power supply.
Should the Do set servo command be before or after the last waypoint?

It will have to be after the last waypoint otherwise it will activate after the previous waypoint. Configure and run it in Mission Planner SITL and monitor the output chanell on the status screen for how it will work.