Rolling Sum

Hi Everyone,

I am fairly new to Power BI and struglling a lot to understand how to add a calculated column that does rolling sum based on Month (String), Cost Center and Cost Element. I have a table like below:

Year	Month Name	CC	CE	Actual	Cumulative Sum
2015	Jan	101	201	12	12
2015	Jan	102	202	13	13
2015	Jan	103	203	14	14
2015	Feb	101	201	10	22
2015	Feb	102	202	11	24
2015	Feb	103	203	12	26

So based on Cost Center (CC), Cost Element (CE) and Month Name I want to do rolling sum of Actuals. E.g. YTD Sum of CC 101 and CE 201 on Feb-15 was 22 (10+12). Since it is year to date rolling sum Jan 15 number doesn't depend on Dec-14 but also need to consider this as I have data from 2013 to 2016.

How do I make this happen. Can anyone please suggest a formula?

Really appreciate your time.

Best,

Keyur Parekh