Function to mess with products in cart

[stabman]

This is a 2-part question. First question should be very simple (but hard for a complete beginner like me) and the second is more trickier.

 

I wish to create a function that can change the attributes of the products in my cart (specifically the customized data).

 

1. I need to know the scope. In which file should I write the function and what other files should I account for when writing it?

 

2. Is there a good format for writing the function, particularly in how to access the attributes?

 

I hope I can get some help here.

[jadelaop]

I'm looking for this too.

[Paul C]

It all depends on when you need to change the data. Is it on adding to the shopping cart or is it when the customer places an order (for example - it could be at any point including after the order has been placed). The timing is very important....

[stabman]

In my case, it needs to be when the customer is in the shipping page of the check out process (the products in question are already in the shopping cart).

[jadelaop]

I need it in the cart summary. I tried to insert js product source in js order source but it doesn't work.