Frequently purchased product analysis using formula/VBA - Is this possible with a formula?

Hi
I'm struggling with a formula or VBA which can return an answer for this statement.
"Given a set of transactions, a set of returning customers and a set of products they purchase, what percentage of products on their transactions always stay the same"

e.g. if Customer X buys 10 products from us, X times a month, and on each transaction there is always the same 5 products, then 50% of the products they purchase stay the same.

I need to get to this percentage on 1000s of rows of data across 1000s of customers and on 1000s of products.

Is this possible?

Thanks!

Rule 1

https://www.excelforum.com/forum-rul...rum-rules.html

A mod will probably come along and ask you to change the subject of the thread as it should reflect a more technical description of the problem, maybe
"Percentage of products that stay the same" rather than "Is this possible with a formula?"

Post a sample spreadsheet with expected results, remove any sensitive data, create a mockup example if necessary.
Use the Go Advanced option at the bottom of the page then scroll down to Manage Attachments as the "paperclip" method does not work on this forum.

Welcome to the forum! Please take a moment to re-read forum rule #1 and then amend your thread title to something that better explains your problem. Changing your thread title is not optional, which means you must change it. Thanks!

Use concise, accurate thread titles.
Your post title should describe your problem, not your anticipated solution.
Use terms appropriate to a Google search - poor thread titles, like Please Help, Urgent, Need Help, Formula Problem, Code Problem, and Need Advice tell us nothing.
Responding to a request to change your thread title by doing so is mandatory.

To change a title go to your first post, click EDIT then Go Advanced and change your title.

No help to be offered, please, until the OP complies with this request.

When you have changed the title, please also give full details of the problem in the body of your post - nobody should have to open an attachment to find out what you want.

you've changed your post title but didn't address what Pete wrote in post #4, is this homework? If so it doesn't mean you won't get help but it does mean we approach the question differently.
AND, Special-K's request to post a sample workbook will also be necessary.