Looks like you are loading a transaction report, and are trying to associate the subtotal line (Cost Center) with the detail lines above it.
There could be a way to do this using a combination of a Textlist string and Find, however, textlist has a 10,000 character limit, so it would only work on a very small list.
I'm mulling this over, but it might be easier to adjust the data in Excel (i.e. an excel formula could find the cost center rows and assign them above), or work with the source system admin to get a more usable dataset (longer term solution, might take some time to coordinate that).
I'll let you know if I come up with anything, I'm intrigued....!
I've been noodling this challenge (just for fun), and keep running into either circular reference issues, or concerns about scalability (i.e. if we used Textlist in some way, or if we had a number of line items, say 10 or 20, that fetched information about the next 10-20 rows in the sequential dataset... but Textlist has a 10,000 character limit (which would probably break fast in this use case), and a fixed number of rows (assumption) usually results in a poor design... unless we're really sure about it..)
Regarding scalability, are there some firm upper limits in your dataset? Specifically, how many Lead Column list items might there be in the list (an upper limit), and how many unique Cost Centers might be in that list? If known, what is the max number of rows in between each cost center?
If there are some limits, we might be able to get creative in other ways.