Scriptable Cart Permission Error

Hi All,

When a customer changes their shipping address, on fieldChanged() I would like to get their new zip/postal code and change the shipping method based on the postcode area. But whenever I try to get the value, it gives a permissions error:

var customerId = nlapiGetFieldValue('entity');  var customer = nlapiLoadRecord('customer', customerId);

Error: Permission Violation: You need the 'Lists -> Customers' permission to access this page. Please contact your account administrator.

I've tried to work around this by adding a Transaction Body field to the form that sources the zip code from the customer. This works initially, but as the custom field has already been sourced, it does not alter if the customer decides to edit their zip code or changes shipping address.