Web Service> Unable to Add/Update the Vendor list for Assembly Items

Customer would want to add/update the vendor list via WS but seems to be unable to do this on Item of type : Assembly Items
 
Note: Vendor list on an Item record is not documented yet as a scriptable sublist, but code seems to work.
 
1. Create custom fields that will temporarily contain values for the Vendor list.
    custitem_vendorid --> vendor
    custitem_vendor_purchprice --> purchaseprice
    custitem_vendor_if_preferred --> preferredvendor

2. Create a script that will pass on these values on the actual Vendor list.
   Setup>Customization>Script New>User Event>
   Script on Event = Before Submit
   Deploy on Record Type = Build/Assembly Item
 
   Note: Triggered within Context 'webservices' upon 'Create' and 'Edit' mode of the Assembly record.
 
Sample script:

function assembly_BeforeSubmit(type, form){
 var currentContext = nlapiGetContext(); 
 if ((currentContext.getExecutionContext() == 'webservices') && (type == 'edit' | type == 'create')) {
                 nVendorID = nlapiGetFieldValue('custitem_vendorid');
  dVendorPrice = nlapiGetFieldValue('custitem_vendor_purchprice');
  bVendorPref = nlapiGetFieldValue('custitem_vendor_if_preferred');
  nlapiSetLineItemValue('itemvendor', 'vendor',1, nVendorID);
  nlapiSetLineItemValue('itemvendor', 'purchaseprice',1, dVendorPrice);
  nlapiSetLineItemValue('itemvendor', 'preferredvendor',1, bVendorPref);
 }
}

 

- Script copies the values from these custom fields whenever the WS call/update is invoked.