I try to migrate our old express checkout process based on PayPal classic API to new RestAPI , but a question has arisen during the new process:

How can I change shipping amount after create a payment and just before execute payment using PayPal restAPI?

Request after create payment:

```html
{
  "intent": "sale",
  "payer": {
    "payment_method": "paypal"
  },
  "transactions": [
    {
      "amount": {
        "currency": "AUD",
        "total": "100",
        "details": {
          "shipping": "10",
          "subtotal": "75",
          "tax": "15"
        }
      },
      "description": "Transaction description.",
      "item_list": {
        "items": [
          {
            "quantity": "5",
            "name": "Item Name",
            "price": "15",
            "currency": "AUD",
            "sku": "sku"
          }
        ]
      }
    }
  ],
  "redirect_urls": {
    "return_url": "http://localhost:56508/PaymentWithPayPal.aspx?guid=77096",
    "cancel_url": "http://localhost:56508/PaymentWithPayPal.aspx?guid=77096"
  }
}

```

request before execute payment:

```html
{
  "id": "PAY-12X5617352981972MKQ64KKA",
  "transactions": [
    {
      "amount": {
        "currency": "AUD",
        "total": "101",
        "details": {
          "shipping": "11",
          "subtotal": "75",
          "tax": "15"
        }
      }
    }
  ]
}
```

PayPal response back after execute payment:

```html
{
  "id": "PAY-12X5617352981972MKQ64KKA",
  "create_time": "2014-10-15T00:51:52Z",
  "update_time": "2014-10-15T00:52:43Z",
  "intent": "sale",
  "payer": {
    "payment_method": "paypal",
    "payer_info": {
      --------------------
-----------------------------
----------------------
      }
    }
  },
  "transactions": [
    {
      "amount": {
        "currency": "AUD",
        "total": "100.00",
        "details": {
          "shipping": "10.00",
          "subtotal": "75.00",
          "tax": "15.00"
        }
      },
      "description": "Transaction description.",
      "item_list": {
        "items": [
          {
            "quantity": "5",
            "name": "Item Name",
            "price": "15.00",
            "currency": "AUD",
            "sku": "sku"
          }
        ],
        "shipping_address": {
         ------------------------------
        }
      },
      "related_resources": [
        {
          "sale": {
            "id": "5KX17441UU9021742",
            "create_time": "2014-10-15T00:51:52Z",
            "update_time": "2014-10-15T00:52:43Z",
            "amount": {
              "currency": "AUD",
              "total": "100.00"
            },
            "state": "completed",
            "parent_payment": "PAY-12X5617352981972MKQ64KKA",
            "links": [
              {
                "href": "https://api.sandbox.paypal.com/v1/payments/sale/5KX17441UU9021742",
                "rel": "self",
                "method": "GET"
              },
              {
                "href": "https://api.sandbox.paypal.com/v1/payments/sale/5KX17441UU9021742/refund",
                "rel": "refund",
                "method": "POST"
              },
              {
                "href": "https://api.sandbox.paypal.com/v1/payments/payment/PAY-12X5617352981972MKQ64KKA",
                "rel": "parent_payment",
                "method": "GET"
              }
            ]
          }
        }
      ]
    }
  ],
  "state": "approved",
  "links": [
    {
      "href": "https://api.sandbox.paypal.com/v1/payments/payment/PAY-12X5617352981972MKQ64KKA",
      "rel": "self",
      "method": "GET"
    }
  ]
}
```