What is the best way to model a rope (joined end-to-end by a coupler) in the shape of a o-ring to obtain the cord length as the ID changes? This rope would be of a specific cord diameter, and I would like the value of the cord length for manufacturing purposes.

I have thought about sheet metal, but the thickness (cord diameter) is solid round stock. Pro-E has an "Evaluate Feature" (see here and here) to calculate the length of a curve. Does SW has an equivalent to calculate the length of a curve, or spline and show it as a dimension?

I would prefer not to use routing as I will need to send these models to a manufacturer. As I need the lenght to be accurate, the flex feature is probably not a good option. I have all the tools from SW2009 Premium available.