Depending on how your data is laid out, you may be able to sort it and then use
data|subtotals.

Or maybe even data|Pivottable.

If you've never use pivottables, here are a few links:

Debra Dalgleish's pictures at Jon Peltier's site:
http://peltiertech.com/Excel/Pivots/pivottables.htm
And Debra's own site:
http://www.contextures.com/xlPivot01.html

John Walkenbach also has some at:
http://j-walk.com/ss/excel/files/general.htm
(look for Tony Gwynn's Hit Database)

Chip Pearson keeps Harald Staff's notes at:
http://www.cpearson.com/excel/pivots.htm

MS has some at (xl2000 and xl2002):
http://office.microsoft.com/downloads/2000/XCrtPiv.aspx
http://office.microsoft.com/assistance/2002/articles/xlconPT101.aspx