WorldPay 'call back' script creation and other bits

Hi, ive developed a website in classic ASP but now need someone to assist with a few other issues, namely helping/creating a callback script from the payment portal WorldPay.

Basically when a customer completes the order and successfully makes payment, WorldPay provide a HTTP post to my website which updates an SQL table with data such as total payment made and WorldPay transaction id etc

This is probably an easy one for someone who's done WorldPayments before.

I also need a few other things doing like form validation, ie checking that two passwords are the same, making sure a checkbox is ticked etc etc.

And finally another issue to add multiple records to an SQL table based on how many items purchased.

More in depth details will be given to selected candidates such as URL and other relevant info.

As I mentioned this is simply to help with the completion of a website already in place, developed in ASP (not .NET) using Dreamweaver with an SQL server hosted on a dedicated server in place.