Get Email in sales order

Hello,

I created a custom record which include a list field from sales order, on the online form custom code (Field Changed Function) I tried to do the following (for testing):

function Test()
{
if(nlapiGetFieldValue('custrecord_order'))
{
alert(nlapiGetFieldValue('custrecord_order'));
}
}

It works well and alert the internal id I selected from the list.

but when I edited my script to load the sales order select (I want to retrieve some fields from the selected sales order), the edited script as the following:

function Test()
{
if(nlapiGetFieldValue('custrecord_order'))
{
var SalesOrder = nlapiLoadRecord('salesorder', nlapiGetFieldValue('custrecord_order'));
alert('test');
}
}

I want to alert(SalesOrder.getFieldValue('emai'); then I want to try retrieve selected sales order items