AddPart function

Hi all

I'm adding some new functionality to the partdetail page. The idea is to hide the current 'add to basket' button and replace it with my own. This button will then link to my own custom page that validates the quantity the user enters, if its invalid then it will send them back to the partdetail page with an error, the problem I am having is when it is valid. I then need to still do the functionality that the old button did, i.e. ad the item to the cart.

I've found the AddPart function in the netpoint.api help file, but a little unsure how to use it, and which one to use, as there are 4 different versions. Any help would be great. Thanks in advance, Andy