The dropdownlist does not change the texfield in multimodelform

Hello to all my greetings after some time without appearing, but I have a detail I would like you to help me solve with the help of this magnificent forum.
The problem is that I am using multimoldelform to bring data to a texfield with ajax in a dropdownlist, but it only changes me in the first product, when trying to add more products they don’t change the texfields, this is my piece of code in the view:

$memberFormConfig = array(
 'showErrorSummary' => true,
'elements' => array(
                    'Codprod' => array(
                        'type' => 'dropdownlist',
                        'prompt' => 'Seleccione',                    
                        'items' => CHtml::listData(TblMprima::model()->findAll(array('order' => 'NProductos', 'condition' => 'CodAlm=634181')), 'Codprod', 'NProductos', 'PreMay'),                   
// 'onChange' => 'javascript:ActualizarCodigo()',
                        'ajax' => array(
                            'type' => 'POST',
                            'url' => CController::createUrl('/contabilidad/transferecias/obtenerProducto'),
                            'dataType' => 'json',
                            ''data' => array(
                                        'incodigo' => 'js:this.value',
                                        'idde' => 'js:$("#Transferencias_CodAlm").val()',
                                    'success' => 'function(data) {

in the controller I have this:

public function actionObtenerProducto() {
        $codigo = $_POST['incodigo'];  
        $destino = $_POST['idde'];
        $producto = TblMprima::model()->findByPk((string) $codigo);
    if ($producto->CodAlm <> $_POST['idde'])
            echo "error";
        echo CJSON::encode(array(
            'NProductos' => $producto->NProductos,
            'Codprod' => $producto->Codprod,
            'PreMay' => $producto->PreMay,
            'Saldo' => $producto->Saldo,
            'Id_UM' => $producto->Id_UM,

Please help with this, I need the textfield to be updated when changing to other products.
sincerely grateful