sales diffrence calc for month and previous month

[srinivasa1]

Hi,

i have a field year contains 2011,2012,2013 and month filter jan,feb,mar etc

i need to calculate the difference sales between current selected year  month and previous month.(ie)

if i selected year 2011 then  feb month then the result should find difference between jan and feb.....

pls,help me out thanks in advance.

[srinivasa1]

Thanks sir,im looking something the way Kaushik Solanki done.is this possible handle in pivot table for mont on mont diffrance.