Create Function To Balance Items That Are Subordinate

I am trying to enhance our estimating spreadsheet. If you look at the example attached it is a snippet of the spreadsheet. What I am trying to do is make column AJ (balanced bid unit) include subordinate items. The way a sub item will be defined is column B (bid item) if column B = S, then its balanced bid unit need to be reflected in the column AJ. I would also any item titled as Y in column B (bid item) to include all listings as S (until next item as Y) in the column AJ totals.