Take a look at Brian Murphy's work at
http://xlrotor.com/resources/files.shtml

Scroll down the page for the XL stuff.

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Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article ,
says...
Hi

I have recently been impressed with the fitting of lines to many thousands
of data points in Excel when displaying this information on a chart, and am
wondering if anyone knows the algorithm that is used to make decisions about
the types of curves (e.g. simple polynomials, splines, Bezier...) used with a
particular data set?

Thanks

Ringo