How can I calculate the length of a cardinal spline?

I am trying to get length of a curve drawn with Graphics.DrawCurve

As stated in msdn library function draws a cardinal spline.

I have yet failed to find any algorithm implementation that would allow me to calculate (or at least estimate with about .01% precision) length of such curve.

I would love to see any help - not necessarily finished vb.net implementation, but something a simple folk can understand (math was never my weapon of choice). Algorithm in any other language as well as step-by-step idiotproof instruction will do.

TIA

I have found some resources on the internet and it now seems that the best shot (or should I say the only one) is to estimate position of points between original points and measure this line segments. Is it really the only way I can do this?

I would LOVE to have some accuracy there.

For those of you interested - look for algorithm in Charles Petzold - Programming Microsoft Windows with C# page 645-646. My search is done.