you have to add hidden form elements for the shipping. For individual items, you can pass the shipping and shipping2.
shipping is the cost to ship each individual item:
<input type="hidden" name="shipping" id="shipping" value="3">
shipping 2 is optional and is an incremental amount for each additional item:
<input type="hidden" name="shipping2" id="shipping2" value="1">
the above example would charge $4 shipping if 2 of the item are ordered.
handling is a charge that is applied to the entire cart:
<input type="hidden" name="handling" id="handling" value="3">
see the paypal reference for more details:
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