Buildable Quantitie values -> Assembly/Build Item Records

Goal: We want to update, via a workflow, a custom item field in our Assembly/Build Item Records called "Buildable QTY" (id: custitem105)

This is where I am at. This is what has been set up thus far.

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1. This is the Script Im using for the work flow. It resides in my SuiteScripts folder. Does this look correct?

 function workflowAction()  {  // Retrieve the current workflow record  var rec = nlapiGetNewRecord();    // Create an Assembly Build in memory  var obj = nlapiCreateRecord('assemblybuild', {recordmode:'dynamic'});    // Set the current item in the build  obj.setFieldValue('item', rec.getId());    // Set the current item build location  obj.setFieldValue('location', 1);    // Retrieve the Buildable Quantity Value  var qty = obj.getFieldValue('buildable');    // Return the generated Buildable Quantity value  return qty;  }