Catalog promotion with the cart promotion bonus "Discount on all products in categories"


I iam trying to edit or modify the catalog ptomotions (or cart promotions) addon for cs-cart.
So it goes something like this:
I would like the produts elegable for the promotion to display discounted and the actual price crossed
When customers buy the product(s) from “Category A”
they get promo notification that they are elegable to get X% discount on all products
from the “Category B”
When they get to see the discounted products from “Category B” the customers see the old and the new discounted prices
This is working with the “cart” promotions but unfortunatly the cart promotion do not display the discounted price until
the checkout page.
Is there a addon that can do that?