Adding a Dynamic Curve into a control Rig

A quick way of adding a dynamic curve into a control rig. I used a distance tool to measure the distance between the two controls. It would be more accurate to use the arc length of the curve.
With you're node editor open, use the mel command: arclen -ch -1
This will add a curveInfo node. Everything else is the same, except you connect the Arc Length to the divide node and not the distance.
Cheers.