How to keep a running sum of a column that changes when I sort it?

I want to have a column summing the total of the percentages next to it. So for example, I have revenue in my first 3 rows of 10, 5, and 1. They make up 10%, 5%, and 1% of revenue and I show that in my 2nd column. I want my 3rd column to show 10%, 15%, and 16% to represent the sum of the percentages to that row's point. If the table wasn't going to be re-sorted and altered I could easily do that by just taking the sum above the cell and adding the % of rev to it.

However, when I re-sort my data, now one of the cells that was referencing the sum above it now has a header above it and is trying to add up a header and gets a value error causing everything after it to have a value error. Also, the previous first row in the column that just took the value of the column next to it still does that halfway down the sheet, completely resetting any sum calculated up until that point.

How can I sum up the % of revenue column as I go along without having that problem when I sort the data a different way? I have attached an excel file with a small, crude example of my problem.