How to retrieve details after payment done in paypal

'Pay pal process Refer for what are the variable are need to send http://www.paypalobjects.com/IntegrationCenter/ic_std-variable-ref-buy-now.html

Dim redirectUrl As String = ""

'Mention URL to redirect content to paypal site
redirectUrl += "https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick&business=" & Email

'First name I assign static based on login details assign this value
redirectUrl += "&first_name=" & Name

'Product Name
redirectUrl += "&item_name=" & "Tour Package"

'Product Amount
redirectUrl += "&amount=" & Totalprice

'Business contact paypal EmailID
redirectUrl += "&business=" & Email
'  redirectUrl = +"&address_street=" & Address
'redirectUrl = +"&address_city=" & City
'Quantiy of product, Here statically added quantity 1
redirectUrl += "&quantity=1"

'If transactioin has been successfully performed, redirect SuccessURL page- this page will be designed by developer
redirectUrl += "&return=" + ConfigurationManager.AppSettings("SuccessURL").ToString()
redirectUrl += "&rm=2"
'If transactioin has been failed, redirect FailedURL page- this page will be designed by developer
redirectUrl += "&cancel_return=" + ConfigurationManager.AppSettings("FailedURL").ToString()

Response.Redirect(redirectUrl)