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