Thanks for the link, but I'm still in the dark on how this will help me. As
you suggested, here's some more info...

The spreadsheet is basically a table with the headings of:
- Visit date
- Client reference
- Client name
There are over 1000 clients included in the table with up to 20 visits per
client in some cases.

There are two steps I need to take. Firstly, count how many visits are
recorded per client. Secondly, list the top 10% of the most frequent
visitors. It sounds so simple but I am really struggling!