Rolling Calculation minus messure

Hello all,

I’ve been struggling all day on this and can’t find a solution.

I’m trying to work out how many workers my factory needs in the future.  I have a total each week that we need, [Weeks backlog efficiency Zoned] and a running total of the number of workers needed [Cumulative], but I want to minus off each value the number of workers we have [Past Staff] .  because we are behind I need to have a cumulative total and move what’s left to be made over into spare capacity next week ect hence the running total.

Cumulative =

CALCULATE([Weeks backlog efficiency Zoned],

   FILTER(ALL('Future Orders'[Yearweek Backlog 2-5]),VALUE('Future Orders'[Yearweek Backlog 2-5]) <= VALUE(MAX('Future Orders'[Yearweek Backlog 2-5]))))

When I minus off the number of workers [paststaff] it only takes it off the first week not every week so I end up with a growing number