Creating new column in power query with multiple criteria

Hi, currently the information that in have in power query is the stock quantity that each branch (Branch A, B, C, D, E) has and the requested qty that is to be transfer from Branch A to other branches.

What I would like is to have a new column (the yellow highlighted ones) in this power query to show the stock (from branch A) that can be transfer to another branches (B, C, D, E), given that the order of the transfer will always be prioritize to B first then C then D then E.

(I could write this through normal formula in excel but this process will be repeated by many times for different dataset so i think doing in power query will be much more neat and flexible)

How can this be done? Thanks for the help in advance

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