Any way to use a custom prop in an equation?

Hello everyone
Here's the background for my question. I often need to model drive chains (roller chain) for the machinery we design. The shape is often
composed of several lines and arcs. To get the length (parametric) in the BOM I used to put a dimension on each segment, create a construction line and make it equal to the sum of all the segements. Then create a custom property named Length and make it equal the the length of the construction line. This is of course a lot of work.
The simplest way would be the following: when you select all the lines at once and use the measure tool, you get the total length. However it doesn't seem possible to pull out this number and make a custom property with it.
So here's what I thought we could do. If I have a config that "cuts out" all but 1 inch of the chain and find the weigth of it, I could go back in the other config and divide the weight by this number to get the total length of the chain. However, I am not able to put custom properties such as mass in the equations (using SW 2005).
So until someone has a better idea, I have to create 2 configs (one with a one inch chain) and use a design table to fill in the custom props using equations.
Thanks in advance for any ideas
Pascal Dufour
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.