List report with item detail

[pn007]

Hi there,
I have a receipt list report that has items and lots. An item can have 1 or more lots. I want to use the Cognos Report Studio ( 11.2.1 )  Total function and total some line items but not others.
Example:
1 item abc has 1 lot with a quantity of 10.
2 item is def has 2 lots with each lot having a quantity of 15.
3 item xyx has 1 lot having a qty of20

I want to display the list and not total abc and xyz, but total def.

report would look similar to below
abc       10  lot 123

def        15  lot 222
             15 lot 225
             ---
             30

xyx        20 lot 555


Any ideas
Thanks