Calculating % Growth dynamically.

Dear Experts,

I have a requirement in a report, mentioned below

Week Week

Products Sales %Change Sales %Change

Prod1 10 NA 15 50%

Prod2 30 NA 25 -16.67%

Selction:: 0CALMONTH

In my query definition, I have mentioned the following attributes

Rows:: Products

Columns:: 0calWeek

Structure

Sales

%Change

Question:: I need to calculate the % of growth dynamcially based on selected month.

Please provide me inputs for this requirement.

Thanks in advance.

Regards,

-Vb