Send data to Related Table in Bill entity Programmaticaly

Hi.

My application is using NetSuite web service,  it gathers fields and tables data for Bill entity and send it to NetSuite.

Recently I get the request that requires such logic : when we send Purchase Order number, the data from Purchase Order entity, which number we are sending for Bill entity, must be automatically uploaded to Related Records table in Bill entity. I attached screenshot where Date and Number.

I need to clarify such moment : Date and Number for Purchase order tab in Related Records table can be automatically uploaded when we send PO Number, while creating Bill entity ? Or it must be implemented in code ? For example for sending data to Items and Expenses table in Bill entity is implemented in code. If data export to Related Records table must be also implemented in code, can you provide code sample how to do it ?

Kindest Regards