Richard,
Thank you. The lectures are helpful. I have done a B Cubic Spline fit where I have extracted the derivative of my curved data. Attached is a PDF showing the results.
As a side note, I have actually coded the process in MathCad 15 to plow through the data accuratly using VBA code. All I do is feed it the vector form of the data, and it will send back the new derivative data vector as I want.