function setEDIPrefix(){
    if(nlapiGetContext().getExecutionContext()=='webservices'&&nlapiGetContext().getUser()==999108){ //user 1646 is my account's SPS user internal id
       var id = nlapiGetFieldValue('tranid'); //gets value from 'document number' field
             nlapiLogExecution('DEBUG','Id: '+id);
                   nlapiSetFieldValue('tranid','EDI'+id); //appends "EDI-" prefix to the NetSuite assigned document number
                }
}