No, it is not possible to netiher manage severals return adresses nor in a dynamic way. However, you can manage a specific redirection with the ID order. This ID being unique for each transaction, during the creation you just have to note this ID down (and to take it into the session itself) and during the redirection to your returnURL, you have to make a #get-orders resquest and verify the order status. A 'closed.completed' status means that all went well. In ohters words, if the status is 'closed.completed' you can redirect to a OK page or a KO page.