Access value sets from Script Base Calculated Value

Hi,
i'm developing an extension that uses these objects:

1) a set a value sets with a set of specific values;
2) a Script Base calculated value

When the user select the value for the custom attributes that use value sets, the script base calculated value has been activated. This script should read all the possible value of a specific custom field and return that value.

The code of the script follow:

/*******************************************************************************
* Licensed Materials - Property of IBM
* (c) Copyright IBM Corporation 2011. All Rights Reserved.
*
* Note to U.S. Government Users Restricted Rights: 
* Use, duplication or disclosure restricted by GSA ADP Schedule
* Contract with IBM Corp.
*******************************************************************************/
dojo.provide("it.gvb.calculatedValue.readCompetenceCenterIdValues");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");

(function() {
    dojo.declare("it.gvb.calculatedValue.readCompetenceCenterIdValues", null, {

        getValue: function(attribute, workItem, configuration) {
       
        var result = "";
        var competenceCenterId = workItem.getValue("it.gvb.customattribute.competenceCenterId"); // here i should read ALL the values for the custom field that use a value set


var itApplicazioniInterne = "it.gvb.enumeration.competenceCenter.literal.l6";
var dataGovernanceUnit = "it.gvb.enumeration.competenceCenter.literal.l4";

if (competenceCenterId.toLowerCase() == itApplicazioniInterne.toLowerCase()) {
result = "IT-ApplicazioniInterne";
} else
  if (competenceCenterId.toLowerCase() == dataGovernanceUnit.toLowerCase()) {
  result = "DataGovernanceUnit";
  }

console.log("competenceCenterId: " + competenceCenterId);
console.log("result: " + result);

return result;

        }
    });
})();


Any idea? Could someone give more info of how read all values returned from the value set?
Thanks!