Self-referencing column

[sethwallin]

Not sure if my title is accurate, but I wasn't sure how to phrase what I need. 

Below is a sample table of data. I want to fill in the [Monthly Position] column using a forumla that would be simple in Excel, but is difficult here given my lack of m/DAX programming knowledge.

The formula would be: (previous month's Position) + (current month's Billing) - (current month's Collections)

The correct results should look like this:

I feel like the answer is easy but I'm just missing it for some reason. Any help is much appreciated!!!

[AlB]

Hi @sethwallin 

Please always show your sample data in text-tabular format in addition to (or instead of) the screen captures. A screen cap doesn't allow people to readily copy the data and run a quick test and thus decreases the likelihood of your question being answered. Just use 'Copy table' in Power BI and paste it here. Or, ideally, share the pbix (beware of confidential data).

You cannot reference a column in its own code. It's a circular dependency. Looking at how your column is built, I believe this would work:

Monthly Position =
CALCULATE (
    SUM ( Table1[Billing] ) - SUM ( Table1[Collection] ),
    Table1[Date] <= EARLIER ( Table1[Date] )
)

Please mark the question solved when done and consider giving kudos if posts are helpful.

Cheers