DAX Power Pivot Measure Help

Hi All,

Not sure if this is the right forum, or if you even take Power Pivot questions, but I know this is a knowledgable group, so I'm going to give it a shot.

I have been working on creating measures to calculate data based on a 3rd table (ie - many-to-many relationship).

Here is the scenario:

Data is all being pulled from P6 database, except the PO list, which is supplied by the client. I want to measure performance against a specific contractor and their specific purchase orders, so I have tacked in a table with that information. My table relationships is shown below. In this case, I am working with the MOD_Site_ID, Q_SMonthly, and POFiltered tables, so ignore the Q_Site_Metrics table:

tables.JPG

Unfortunately, Power Pivot data models are only capable of a one-way relationship, but I have been able to create measures that allow me to filter by purchase orders, and here is how that works:

First, I create a measure on the category

AC Measure.JPG

Then I use that measure to create a second measure that will filter against the PO table

ACbyPOMeasure.JPG

So, that is working well. But the final step I'd like to take is to create a CUMULATIVE measure that can be filtered by PO. This allows me to chart the metric as it grows across the months. Here is an example of a cumulative measure works on another table in my project, and you can see that each successive row adds this months value to the row above it:

Finexample.JPG

I'd like to do that in my measure that filters by PO, but can't get it to work. Here is what is happening:

doesntworkhere.JPG

I've tried writing this measure several different ways, but no matter how I approach it, I haven't been able to solve it.
Here is the measure as it is written at the moment:
ACCumbyPO:=CALCULATE([ACbyPO],FILTER(ALL('Calendar'),[Date]<='Calendar'[Date]),VALUES('Calendar'[Year]))


Any DAX lovers out there willing to weigh in?

Awww, no takers? Unusual for this group. I'm still wrangling with this, and haven't figured it out yet, so I'm open to all suggestions!
Kirstin