How to dynamically split a list into equal parts?

Hi, I have a list of customers (ColA) and depending on the total amount of customers I want to "split" the list into equal groups (let's say steps of 10%) and flag these groups. So having 20 customers and using steps of 10%, the first 2 customers are grouped together and flagged in ColB as 10%. Customers 3-4 are grouped (20%), 5-6 (30%) are grouped etc. ![alt text][1] When this list increases to 100 customers it should group the first 20 customers (10%), 21-40 (20%) and so on. I'm expecting some form of the streamstats command here, but can't find the solution. Thanks in advance Heinz [1]: /storage/temp/157216-decimals.png