Running Total in Matrix

Hello guys,

We are currently struggling with a running total topic. 

Let's assume you have a table with the following columns:

balance_sheet_code,

as_of_date,

accounting_period,

cash_flow

We managed to create a running total on accounting periods (accumulation) IF the "accounting_period" field is on the column in the matrix. 

In case we simply put the "as_of_date" on the columns in the matrix and create a slicer to select the "accounting_period", then the accumulation does not work. It simply displays the value for the single accounting_period (non-accumulated) in the matrix.

The goal is that we select i.e. "accounting_period" = "10 days" in the slice and the matrix shows accumulated numbers (of cash_flow)  per "as_of_date" in the matrix.

Matrix layout is:

balance_sheet_code on the rows, accounting_period on columns, cash_flow in values and as_of_date in slicer --> all good
balance_sheet_code on the rows, as_of_date on columns, cash_flow in values and accounting_period in slicer --> issue

any help is very much appreciated.