Get any point's Coordinates in a Curve

[Uwe]

Hum have you some link that explain how to calculate something like this.
With some points we have a line and it's simple to calculate a coordinate on the line, but with a large number of points it was not so easy or i'm wrong?

You are: each coordinate is between 2 curve points and this is always ( beside of splines ) a simple line. The number of curve points doesn't matter.

Uwe