Pivot/Table with values left to do within project

hello, 
i am trying to deal with designing Pivot (or Table) that would show values left dealing with. 
Long story short:
Got list of Accounts that has requirements to proceed in project. Table in Excel looks like this:

What I have been asked for it to create report that would show of course charts etc to help read progress but as well to show decreasing value every week from whats left to do, something like that:

and then of course visuals charts with trends lines etc.

What my issue is - I got trouble to create measures that would be lowering when using forecast table as date hierarchy and showing whats left to do similiary like on screenshot2 (which is from Excel) but within BI.