How to load or select custom address in Multiple Shipping Routes enabled Sales Order

I create a customized csv import suitelet. It reads date from selected csv file, create sales order with ('ismultishipto',"T"), and create custom address for each line item. I used for loop to check if it is same address. When it happens to be same address, I need to select shipaddress. It seens that custom shipaddress is not available to load. I don't want go back to edit shipaddress after salesorder is created. How can I select shipaddress to a custom shippingaddress by script?

Here is my code to create custom shippingaddress:

var subrecord = newSalesorder.createCurrentLineItemSubrecord('item ', 'shippingaddress');
subrecord.setFieldValue( 'label', itemArray[i][nameIndex]);