Basically, I am creating a routing of tubing on an assembly of mine.  I know the tubing outer diameter and I have 2 3D splines that are encroaching on each other as they go from point to point.

Is there an easy way to add a control to control the distance between these 2 splines?

The closest that they come to each other is just under 6 mm and I want them to be at least 8 mm apart.

Right now, the only controls that I have on them are coincident constraints on the end points of the splines and tangency constraints between the splines and the lines I want them tangent to.

Edit: I did do some editing on the splines with the tangency and got it to where I want it.  But the question stands.....how can I control distance between 2 splines?