Varience between Month Data

[johny.cbi]

I have a list report and columns are Months ( Jan to Dec) and 've value prompt for year (2005,2006,2007,2008)

If we select Year it will display the Total data from Jan to Dec

I used the Varience/caluclation for (FEB-JAN, MARCH-FEB, APRIL-MARCH etc... for all the years) to get difference between current month and previous month

my question is

If I select Year 2007

I want the varience between  2007 JAN and 2006 DEC

for  2006
I want the Varience between 2006 JAN and 2005 DEC  etc.....


Thanks for the answers

[almeids]

What is the question/problem?
There's nothing special about the January calculation; you're just not going to display the December data item on the report.  Make sure your filter includes December of the prior year as well.
Or is the issue that the database table includes a single year per record?  If that's the case you need your filter to bring in both years and must conditionally calculate the data items so that they only include values from the latter year: if (year='year1') then (0) else (jan_value) etc.