VBA Excel add-in utilities and worksheet templates

Fourth-order, zero phase-shift Butterworth low-pass filter & adaptive butterworth filter (version 2 -06 may 2007).  Download: pdf manual , Add-In for Microsoft Excel (save as .xla)

Polynomial curve fitting, interpolate, extrapolate: XlXtrFun™ Extra Functions for Microsoft Excel.  Link to website  (Advanced Systems Design and Development, Red Lion, USA). A shareware alternative that also works on Windows XP x64 is available via the SRS1 Software website.

Compute standard ellipses, confidence ellipses and prediction interval ellipses.  Download: Excel 2003 sheet with VBA macros (save as .xls)