How to set a new waypoint after reaching the previous one in a Simulink flight simulation

I have a PID controller for a quadcopter. Rather than inputting a time-series trajectory for it to follow, I would like to input a list of waypoints for it to visit. I have coded a boolean variable in one of the functions that turns True when the total distance to the waypoint is less than an arbitrary threshold. How do I connect this to the list of waypoints to specify that the aircraft can start heading toward the next one as soon as this boolean variable turns True?