Change move speed

I’m using a simple script that reads waypoints over the ethernet. So, I send a waypoint request to the PC, it responds with 6 target motor positions and a velocity, to which the robot moves via a movel() instruction. Ideally, the user can give an updated velocity via the PC were the set point was send, or via an external control on the robot analog or digital inputs. How could this be achieved?

I’ve seen a code sample for adjusting the speed slider, but that feels awkward and in the future I may need to alter not only speed but other stuff, too. Guess it amounts to be able to interrupt the current move via thread or something and then simply do a new movel(). But can a thread abort an movel() in progress?