This can be tricky since Tableau is not really designed to work like Excel. In any case, are you able to attach the Excel file so we could look at it and think about potential solutions?
That's not row-level calculations. That's doing calcs across the table. Row-level would be taking [Sales] and multiplying it by [Unit Price] and getting a sales dollar amount within each Container, for example.
What signifies the break between Container F and G?
Keep in mind that Tableau is not Excel. They have different methodologies and approaches in the way they process data. Tableau is going to want to treat all containers the same way. We can group them and do operations among group values. And we can use table calcs to grab values from the first and last members in a dimensional series (and other offsets as well.)
I would need a whole lot more info (and really, a sample workbook) to give much more of an answer than this.
I see you added a sample workbook. Other than saying that you need to subtract one value from another, can you explain your ultimate goal? What is it you're trying to accomplish? What is the reason for subtracting these values? The answers to those questions, I think, should help us to better understand how to attack this problem.