@acer That is a great suggestion as well! I will try it now and see how it is.

Yesterday I implemented your first solution in my code and managed to solve my final problem (which I wanted to have solved by today) and had a first introduction on how functions work in maple along the way so ... all in all star! :)

It took me a while to understand everything that you wrote but now it all makes more sense.

You "dissemble" the output of the Spline only to "reallocate" the intervals with their respective derivatives.
It is very logic and at the same time genius.

Many thanks, acer! You taught me a lot with your answer :)

Best,

dbachito