your description is still laking enough detail, so I will assume that the details from my previous reply are what you are trying to accomplish.
on the calculations tab, create a new calculation as:
name: shipPrice
[Weight] * 1 + (abs([Quantity] >1)?([Quantity] - 1) * ([Weight] * 0.50):0)
and on the shipping tab, use the "Subtotal for any column" trigger:
if the sub total of "shipPrice" is ">" a value of "0"
and for the calculation, use "Based on column subtotal"
Subtotal of column "shipPrice" "plus" "0"