How to implement merchantcalculationurl in google checkout in my application?

I send the shopping cart request to Googr le checkout sing the following code, in the code behind of the Google checkout button. What is the next step after this? HOw do I read the response for this request. I also need to get the shipping information. HOw do I redirect. Please help. thanks

Dim request As CheckoutShoppingCartRequest = New CheckoutShoppingCartRequest("merchantid", "key", EnvironmentType.Sandbox, "USD", 120)
        request.AddItem("ITem 1", "desc 1", 2.0, 1)
        request.AddStateTaxRule("CT", 0.06, True)
        request.AddStateTaxRule("MD", 0.05, False)
        Dim cart As Byte() = request.GetXml()
        cart = request.GetXml()

        Dim res As GCheckoutResponse = request.Send()
        Response.Redirect(res.RedirectUrl, True)
Who is Participating?
Meir RivkinConnect With a Mentor Full stack Software EngineerCommented:
follow this tutorial:

it describes exactly what to do and how.
TrialUserAuthor Commented:
The document does not explain the Merchantcalculations api and notification  API. I want to know how to write these pages. Thanks

This section is from the document. I want toknow how to implement these.
Merchant Calculations API -

Create an .aspx page that will handle merchant-calculation-callback requests from Google Checkout. This page should parse merchant-calculation-callback requests and then call the methods that you use to calculate taxes, shipping charges, and discounts for coupons and gift certificates.

The classes and methods in the MerchantCalculations directory of the sample code distribution may help you to develop the .aspx page. Please check this document in coming weeks for more detailed instructions about how to call and use these methods.

Use the URL for your .aspx page as the value of the <merchant-calculations-url> element in your Google Checkout API requests. Google Checkout will then send merchant-calculation-callback requests to your .aspx page.

Notification API -

Create an .aspx page that will handle notifications, such as order state change notifications, and then send the information in those notifications to the appropriate internal systems.

Note: The .NET sample code distribution does not include classes or methods to process notifications or to send notification acknowledgments.

Enter the URL for your .aspx page in the API callback URL field in your Google Checkout settings. To locate this field, log in to your checkout account and click the Settings tab. Then click the Integration link in the menu on the left side of the page.
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