570960 quantity discount problem

We got MODULE CAT QVB DISCOUNT (category discount module) in our webshop but got issue the quantity for whole category. Means if we got buy 20 items from this category. User buy 19 x product of 0.35 cent, and 1 x 20.000 it will cost me lot of money. This cannot be the meaning of such o module. So we want it modified, or installed a total new module where its possible to do similar, but have it enabled for similar products only. so if we say 25 % from this category for similar items only We want this to displayed above the categories , shopping cart and product info page. Just like we got it now.