Referencing a specific data value

Is there a way to reference the initial data point in a table? For example, I have a data table of average weekly customer products.

I want to now have a table that shows the weekly average as a percentage of the first value for each customer.

So ideally it would be in this same format, but the values in the table would be expressed as a percentage of each respective initial value. So, for customer 183, the values would be 100%, then 87.37%. Customer Grimco's values would be 100%, 100.5%, 100.7%, 100.8%, etc.

Is there a simple way to do this? Maybe somehow viewing by a custom expression? I can't figure out how to reference a specific value for each column. I might just have to go in with SQL.

Thanks in advance!

Hi @ana
It would probably be a little easier to understand with the raw table instead of a pivot, but I think you would have to do something like this in SQL - perhaps the CTE article can give you some help:
It would require doing a lookup for the first value, which the GUI isn't able to do easily.
You can still create most in SQL, so you return raw data, which you then visualize in a GUI question, so you have more functionality like filtering.