Kevin,
I don't think the Excel version matters. Excel was limited to 16
regressors (at least in Excel 97 and I doubt it has changed). Others
have also discovered the limitation. I'm assuming you are talking
about regressors or variables not data points as you indicated. I
don't think there is a limit on data points other than 65,536 (# rows
on a sheet).
I've never used it, but you might look at an add-in for Excel I found.
Apparently it can handle 256 regressors limited only by # columns in
Excel.
http://www.analyse-it.com/faqs/21000.htm
I usually use the LINEST function (limited by 16 as you know). I've
never tried to call it within VBA, but expect the same strange limit
will apply. You could also use something external like Minitab.
Finally, you can do the regression using basic statistical methods
instead of a function that does it for you. Personally, I'd rather
buy the add-in than a statistics book!
Happy Holidays,
Steve Hieb