Cumulative total based on week ending date

marcritchie - You should be able to do this:

Actual Booked Cumulative = 
VAR __MaxReportingDate = MAXX(ALL('Reporting Date',[Week Ending])
RETURN
CALCULATE (
    SUM ( Replicon[Actual Booked Period] ),
    FILTER (
        ALL ( 'Reporting Date'[Week Ending] ),
        'Reporting Date'[Week Ending] <= MAX ( 'Reporting Date'[Week Ending] ) &&
          'Reporting Date'[Week Ending] <= __MaxReportingDate
    )
)

Otherwise, would need to see sample data and example of the issue you are describing. Not really enough information to go on, please first check if your issue is a common issue listed here: https://community.powerbi.com/t5/Community-Blog/Before-You-Post-Read-This/ba-p/1116882

Also, please see this post regarding How to Get Your Question Answered Quickly: https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

The most important parts are:
1. Sample data as text, use the table tool in the editing bar
2. Expected output from sample data
3. Explanation in words of how to get from 1. to 2.