Wire feeder control

The current task for the welder project is to separate the control of the extruder (wire feeder) from the software so that the speed can be controlled from an analog potentiometer.
The idea is to have the slicer software output on or off commands to the wire feeder and then I can adjust the speed of the wire by eye and feel. A little bit of an "old school" hands on fix. The long view advantage to this strategy will be the ability to pulse the wire.
I'm trying to use an Arduino for the task. The programming language is not intuitive to me yet so there's a bunch of head scratching going on. 

Image courtesy of Arduino Knowledge Base