Setting value on custom transaction field for Sales Order

The problem I'm trying to solve is to get the actual unique item # (itemid) to display on the Sales Order when printed out in PDF version. The customer gets a confirmation email upon a weborder (with the unique itemid and a description) but the default Netsuite PDF layout for sales order only displays the description.

I created a custom transaction colum field called 'custcol_cust_tcol_item_num_pdf' with the intent to source this directly from the standard transaction field item (itemid). This custom field would hold the unique item # which I then expose on the PDF layout so I can print out the item # on customer orders. I want to invoke this code once the user saves the Sales Order so as a SAVERECORD or BEFORESAVE function. My code looks like this: