Paypal Subscriptions to our project

We need to implement PayPal subscription payments to our C# .NET webproject. Here is a logic it needs to be implemented: 1) Visitor enter his account 2) Click buy button 3) Forwarded to paypal page 4) Finish his subscription 5) PayPal send's back notification to our service 6) If payment successful project executes SQL query (will provide later) 7) If payment declined - no actions done 8) Next month once paypal charges account paypal sends call back to our project - simple SQL query needs to be executed at that time too.