Need Help with Shipping in Mals-e Shopping Cart System

Hi,

I have to handle the following scenario for shipping of my sale items
in an online shopping cart system. I am currently using Mals-e, but I
cannot figure out how to make it support this scenario...

Sale Item #1 (books) - $4.00 first item, $1.00 each additional
Sale Item #2 (posters) - $7.00 first item, $0.00 each additional

Can anyone suggest a way to make Mals-e support this or another
shopping cart system that would? I am also open to hearing about some
recommended solid client-side coding methods that I could use so that I
could calculate my own shipping and send it over to Mals-e for
processing.

Thanks in advance!
Kelly