Excel actually uses Bezier curves, though they can be approximated by
splines. Look for the Smooth_curve_bezier_example_file.xls download in the
bottom part of this page on Brian Murphy's web site:

http://www.xlrotor.com/resources/files.shtml

- Jon
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Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
http://PeltierTech.com
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"IAN" wrote in message
...
I would appreciate your help in the following issue:

We like to know what function the Excel developpers have used in Excel for
Charts/XY(scatter)/smooth lines. It iseems to us that it is a B-spline but
there are many of those around. Could you please provide us with the exact
spline function used for interpolation in this Excel option and possibly
the
code

Thanks a lot in advance
Ian