How to accumulate data monthwise but starting fresh every quarter
I have a set of data for frquency and coverage by months from May-11 to June-2013. I have created a pivot table for this in qlikview. Now i want the cumulative sum of data monthwise but starting fresh evry quarter of the year. Eg: In month of May-11 i should have the data for May-11. For June i shuld have may+june. For July i should have May+june+july. Now again for august i want data for only august. for september i want data for august and septembe and so on.