Non-monotonic many points Cubic Spline routine in Pascal?

I would really like to know how to draw a smooth curve through points
representing the contour of a curved shape.

The routine that produces the results I desire is called a natural cubic
spline.

This is the method used by Design-Cad when one traces a curved shaped
with a digitizing tablet and puck.

I am not a math wiz. Pacal is the only language I know.

TIA

Chuck Baggett
http://www2.misnet.com/~unforget