The simplest way is to use the TREND or LINEST worksheet functions.
http://people.stfx.ca/bliengme/ExcelTips/Polynomial.htm
shows how to specify polynomials to them. If you are overfitting the data,
you may have numerical issues with versions prior to 2003. Beware in 2003 if
a coefficient happens to be exactly zero.

Alternately, Tushar Mehta has enhanced VBA code by David Braden to extract
coefficients from the chart trendline.
http://groups.google.com/group/micro...da30f29434786d

Jerry

"Matt J" wrote:

I used the "add trendline" in Excel 2000 to do a 3rd order poly curve fit of
some data. Works great and I chose the "display equation" feature so I can
see the resulting polynomial coefficients, BUT, how can I automatically use
these coefficients in further calculations? Are they, can they be, available
in cells? Used elsewhere, for a slope (derivative) function for instance?
--
Matt J