XLMTH30.ZIP contains an Excel dynamic link library and a workbook
with sample worksheets. The DLL called XLMATH.XLL contains custom
functions and dialogs to enable the user to perform data smoothing
and fitting. XLMATH.XLL also contains a custom function for 
diagonalizing real symmetric matrices. XLMTH30.ZIP replaces previous
versions. The last version uploaded was titled XLMATHPA.ZIP which was
a patch for XLMATH v2.2.