Script to extract spline in center of a tube

Hi,

If someone wanted to take a crack at this, would be much appreciated.

Basically i'm looking for a script to extract spline in center of a tube.

What i'm doing now is loop selecting an edge and converting to a spline to run a new extrusion along, but I need the spline to be in the middle of the tube, so i'm currently moving the spline manually in position.

thx