Process Extension Scenario(SalesOrder -> Invoice Request)

Hi, experts.

     I am having trouble with the process Extension Scenario.

    1. I created a process extension scenario like the following.

2.I added an extension field to the scenario in the SalesOrder.xbo's definiiton. Just like this.

[Label("From Sales Order")][Scenario(SalesOrder_XS_Test)]element N_SalesOrder_XS : LANGUAGEINDEPENDENT_EXTENDED_Text;

3.I added the extension field to the General Information section group of SalesOrderQAF.
4.I also added the extension field to the General Information section group of CustomerInvoiceDownPaymentQAF

5.I saved a new sales order with some data in the newly extension field.

6.I created a new down payment request from that sales order.

But the annoying prolem is that the data in the new extension field cannot be transfered from Sales Order to invoice request.

Regards,

Fred.