well, setting a per item shipping price is a little different.
you need to add a new cart column in the eCart object for shippingPrice, and add this column into the products database as well.
in the add to cart button server behavior, bind the shippingPrice cart column to the shipping price column in the products recordset.
on the calculation column of the eCart object, you need to create a new calculation called TotalShipping:
[shippingprice] * [Quantity]
The shipping rule you create on the shipping tab will still use the same trigger, but the calculation will be:
Based on Column Subtotal - Subtotal of "TotalShipping" "plus" "0"