Using worldpay questions

Hi there,
I am using worldpay as the payment provider.

I have run the checkout wizard and my pages have been created.

in the merchant contol panel for worlpay, i am unsure as to what page to set up for the payment response url?

i gather that it can take up to 4 days fro the payment to be processed, in paypal it has the IPN feature, does worldpay have something similar, i would like to store the order in the database (which i have used the default setup from the ecart wizard 2 tables order and orderdetails) when the payment is recieved i would like to have a payment recieved column set to true once the payment has been recieved.

how does worldpay determine wether to go to checkout sucsess page or checkout fail page? as i can only put 1 url in the checkout response on the worlpay merchant control panel.

or do i need to create a page to process the repsonse that redirects to the appropiuate page depending on the response?

and if so how would i go about doing it?

ive looked on the help for the extension but there does not seem to be any guides for specific gateways other than paypal and sagepay/protx

thank in advance for advice/help