I want to set the value for the multi-select with existing values in that field. (i.e) If the Filed has the values "A , B" means I wants add the New Value "c" with Existing Values So, Result would be "A,B,C" .
I used "N/Record' Modules SubmitFields API to set the value for the Multi-select Field like this
CODE : SuiteScript 2.0 version :
Initial Code:
var strArrayValue = new Array();
    strArrayValue [0] = "A";
    strArrayValue [1] = "B";
    strArrayValue [2] = "C";
record.submitFields({
         type:'purchaseorder',
         id:56,
         values:{
         custbody_multiselectfield: strArrayValue 
         },
         options: {
            enableSourcing: false,
            ignoreMandatoryFields : true
          }
});
It is showing the error like this : "you have entered an Invalid Type Argument :arg 4"
Updated Code :
 var strArrayValue = new Array();
        strArrayValue [0] = "A";
        strArrayValue [1] = "B";
        strArrayValue [2] = "C";
   var PORec = record.load({               // Loading Purchase Order Recod
                type:"purchaseorder",
                id:56,
                isDynamic: true
                 )};
        PORec.setValue('custbody_multiselectfield',strArrayValue ); // Setting Value (Array List) for Multi-Select Fields
        PORec.save();    // Saving Loaded Record
It is also showing the error: " Invalid custbody_multiselectfield'reference key 31567,31568 "
But if I add an Value as an String instead of String Array it is setting only single value (i.e) overriding the previous values. Ex: Multi-select has only the "C" value instead of "A,B,C" Values.
Can anyone help regarding this question.
 
     
     
    