Integrating paypal in asp.net app big problem

 Hi,
 I've used classes from this article:
http://www.west-wind.com/presentations/PayPalIntegration/PayPalIntegration.asp
to integrate paypal payments to my asp.net app, 
in the PayPalHelper I set SuccessUrl = Request.Url+ "?PayPal=Success"
BUT On Success I receive http://my_site/products/OrderForm.aspx?merchant_return_link=Return+to+AspNetSource.com
Which totally doesn't work as expected.
 I someone has integrate paypal from the link above, I'll be very thankful to hear his opinion.
 
Thanks in advance,
Tihomir Ivanov

...