=countif(sheet1!A:A,"=01/01/1985")-countif(sheet1!A:A,"31/12/1995")
would give you the count of people born between 1985 and 1995 inclusive and
listed on sheet1 assuming birthdate is in column A (as an example)

from this, you should be able to figure out how to address other sheets.
Perhaps a separate sheet where you gather data from each individual sheet
and consolidate or combine formulas.

--
Regards,
Tom Ogilvy



"Steve Wylie" wrote in message
...
I have a workbook going across several dozen sheet tabs, containing
demographic information on about 10,000 people (I work for a local
authority
- I'm not some direct marketer or spammer or anything!)

One of the items of data is their date of birth. I need to use this in
Excel somehow to extract percentages & counts of how many people fit into
certain age groups (18-30, 31-40, 41-50 etc).

Is this possible without moving the data out of Excel, using formulas? We
have a survey/data analysis program but I am loath to transfer all that
data
unnecessarily when it could just be done in Excel...

Thank you for any help anyone can give.

Steve Wylie
Canterbury
United Kingdom