Cumulative sum in pivot

[#1]

Hi, i have a pivot table with category in rows and months in columns. I need a cummulative sum by months. Without accumulation, i simply have =sum({$<[Category]={'Books'} >}Sales) etc. How to change it to accumulation by months?

	January	February	March etc
Books	5	6	2
Jewelery	3	4	5

need to get

	January	February	March etc
Books	5	11	13
Jewelery	3	7	12

[Gysbert_Wassenaar]

Depends on what you need. Perhaps using the function above() or before() is enough for your situation. See Calculating rolling n-period totals, averages or other aggregations for more information.

[#3]

I need a simply measure just like in example in my post.

If you need more details, the category here I have as expressions: =sum({$<[Category]={'Books'}>}Sales) and =sum({$<[Category]={'Jewelery'}>}Sales), Month name is a dimension

Sth like example attached below, but instead of date, i have month name