DAX/Power Pivot: Calculate 75% Expended Date from Cumulative Total - excel

Question

I have three tables that contain cost: Forecasted Cost, Actual Costs, Invoiced Costs. Each has an "EAC Filter" column for a Y/N of whether to include the cost in an Estimate at Completion, which automatically changes over time and/or as data is added. Here are examples:
EAC from the three tables can be calculated as follows:
Total Cost = Sum(Forecast[Cost])+Sum(Actual[Cost])+Sum(Invoice[Cost])
EAC = Calculate([Total Cost],EAC_Filter[EAC Filter]="Y")
I have a budget at the "Account" level, which could also be rolled up to a "Dept" level budget.
I need a measure for my Power Pivot table which will display the week at which costs have exceeded, or are forecasted to exceed 75% of the budget, using some sort of a cumulative cost, combined with the max week where cumulative cost >= .75 * Budget.
The weeks are numbered through the year as follows:
Thanks for your help!

Answer 1

Given an EAC measure which sums the cost per week,
EAC = CALCULATE(SUM(Forcast[Cost]) + SUM(Acutal[Cost]) + SUM(Invoice[Cost]),
EAC_Filter[EAC Filter] = "Y")
You can create a Cumulative Cost measure as follows:
Cumulative Cost = CALCULATE([EAC],
FILTER(ALL('Calendar'), 'Calendar'[Week] <= MAX('Calendar'[Week])))
Using this, we can create a measure that predicts the week the cost exceeds 75% of the budget:
75% Week = MINX(FILTER(ALL('Calendar'), [Cumulative Cost] > 0.75 * SUM(Budget[Budget])),
'Calendar'[Week])
Here's what the relationships structure looks like: