The ics_paypal_refund service:
nEnables you to perform a full refund for an order.
nEnables you to perform multiple partial refunds for an order.
When you request ics_paypal_refund, you must include the following fields in the request:
nics_applications
nmerchant_id
nmerchant_ref_number
ngrand_total_amount—The amount of the refund determines if it is a full refund or a partial refund.
npaypal_capture_id
npaypal_do_capture_request_id—This value determines which capture will be refunded.
npaypal_do_capture_request_token
Additional fields are optional. The required and optional fields are described in API Fields.