ASP Paypal Integration

I have a custom .ASP shopping cart (not .NET) and I need to integrate PayPal API into the shopping cart. I will want the paypal process to proceed and confirm before the shopping cart stores the data in the database and send e-mails. All of this is already working on a couple of live carts with merchant accounts. I have just not integrated Paypal yet. The cart is designed to store a transaction ID returned by the merchant account for a successful purchase. I dont know what Paypal calls this ID but I assume it will be something similar. And you will be able to stick that in the database.