Yes, Create a shipping amount column in the cart object. in each products add to cart button, set the column to the flat rate that will be charged to ship that item.
next create a new calculation of:
[shippingAmount] * [Quantity]
To return the shipping amount for the quantity orderd. name the calculation TotalShipping
Then create a shipping charge rule that uses the trigger Number of unique items in the cart is > than 0.
For the calculation use:
Based on Column Subtotal:
sub total of column [TotalShipping] [plus][0]
