How to get the running total for the last month in the chart in cognos 10.2.1 da

[xyz]

Hi Gurus,

I have a requirement to develop a combination chart report in Cognos 10.2.1 data source is relational model, the chart has to display data for one year from current date, display month concatenated with year on x-axis and with open and closed cases as lines in series along with total open cases bar also in series. I am extracting month and year from date column (YYYY-MM-DD).

30  |
20  |
10  |
5    |
0    | 
      ______________________________
      Mar-14 Apr -14 .........................  Mar -15

Issue I am facing here is, the bars has to do sum (Open cases - Closed cases)  and running total on the sum (Open cases - closed cases), problem here is for Mar -14, if open case = 20, closed case = 5 then

bar chart calculation is Feb -14  Open cases + Mar - 14 Open cases - Mar 14 Closed cases

I created two separate queries one for open cases which will give me 13 months data and one query for 13 months for closed cases then did union and got the open cases and closed cases and did sum for Feb -14 month to Mar -14 but unable to do running total on correctly from Mar -14 month on the bar charts.

How will I achieve the above requirement in cognos report studio.


Thanks & Regards,
XYZ