Year over year analysis in cognos

My requirement is  that:
whenever i pass a year through prompt i should get a report with details of selected year and previous year.

To achieve that create a two data items similar to below expression
date item :current Year

if(?p_year?=[ Year column] )
then
([Measure column])
else
(0)

date item2: Previous year

if ([Year column]=(?p_year? )-1)
then
([Measure column])
else
(0)

these two will give you the desired results.