Can anybody please help me how to generate group wise total in crosstab rep

Hi i am working in business objects can somebody help me out, how to generate a crosstab report with groupwise totals as given below

A B AB C D CD

Product_1 20 30 50 40 20 60

Product_2 70 20 90 30 20 50

I want AB and CD calculated columns in this crosstab report

Pls help me