I Dont Get It - Paypal IPN - Do you understand?

Can you figure this out?

I wanted to sell a few different products (on different sites) with Paypal Directly. But how can I send each one to its own Thank You page when paypal only allows 1 IPN URL. How is this even possible?

 

The best way to do that (I feel) is add a parameter or variable to transaction specific to the item. When your ipn url initially loads or captures the paypal return data
(you need server side programming for this, php asp.net etc) instantiate a function to handle the specific item.

For example with improper syntax

Sub Page_Load  ' thank you page has first loaded
CapturePaypalData
End Sub

Code (markup):

Sub CapturePaypalData

'Paypal return variables through their IPN to your IPN page located on your server.
Name =paypal_returned_name
Address=paypal_returned_address
[B]Product[/B]=paypal_returned_product

If[B] Product.Contains("Car")[/B] Then
Response.Redirect("http://mysite.com/thankyouforbuyinga[B]car[/B].html")
End If

If[B] Product.Contains("Horse")[/B] Then
Response.Redirect("http://mysite.com/thankyouforbuyinga[B]horse[/B].html")
End If
End Sub

Code (markup):

You can do the same thing with donate buttons etc.
Have one thank you page that reads the query string then in your button codes add a return on success that looks like such.

[URL]http://mysite.com/thankyou.aspx?Product=Car[/URL]
or 
[URL]http://mysite.com/thankyou.aspx?Product=Horse[/URL]

Code (markup):

By doing that you can just change the page_load (or whichever method for your language uses to start processing) on your thankyou page
to

If Request.QueryString.Contains("Car") Then
Response.Redirect("http://mysite.com/thankyouforbuyinga[B]car[/B].html")
Else
Response.Redirect("http://mysite.com/thankyouforbuyinga[B]horse[/B].html")
End If

Code (markup):

This is the concept that I use and the code shown is only to demonstrate my concept. It will not parse as is.

 

Thanks for taking the time to explain. Does your example apply to products on two different URL?