Complex Problem with shipping costs - Help!

Hi All

I have a complex problem with the CE version when I want to set shipping costs for each item.

I have established weights & sizes for all articles and I have also established a list of possible modes of shipping.

For the most partt I have the shop working fine, offering up users options with a drop down menu showing the shipping options where they exist. However there are a few articles that are resisting my wishes.

Can some one help me with an ABC on how to establish customer shipping costs (options) based on how many they buy. Usually the weight is the determining factor.

I have been trying different things with:

-Shipping Methods
-Shipping Cost Rules
-Administer Products - various

It really is a mind bender

Thanks Don