Convert position of a point on a spline to another spline which is connected

[ATHellboy]

As long as the lists you are accessing have at least one element, yes that code is correct

if the value is not in the valid range, clamp it to the valid range (0;SplineLenght)

No, I don't think so if you get what I want exactly.
I mean for example I have a object in Absolute Position of 10 then according to this position I have a point in 15 unit of Absolute Position behind this object. So this point has Absolute Position of -5. Now I want to get world position of this point and then convert it to the Absolute position of the other spline which is connected to this spline.