I've not seen your workbook and sample data set yet, but I would like to add a comment for your consideration:
By concept, every quartile has the same number of products if you are calculating quartile at product level of detail, as you mentioned in your post.
... For the division of quartiles, I want the number of products that make up 25% of the total revenue for that year to be in Quartile 1. I want the next 25% to be in Quartile 2, etc..
I will take a look at your workbook
I must not have made it clear what I mean by Quartiles. Basically what I want to do is determine which products are high sellers over the years. Is most of the revenue coming from specific products? So, I want to determine what percent of the total revenue each product makes up for that year. (ie product 1 is .02% of total revenue) Then I want to take the highest percentage products (descending sort) and add them up until they make 25% of the total revenue for that year and put them into Quartile 1. Then use the same method, except it would be from >25% to just over 50%, and label those products as being in Quartile 2 for that year, etc…
I hope that helps to clarify what I am trying to accomplish.
Thanks for the quick response,