BDC problem in F-30

Dear All,

I am writing BDC on F-30. On the last screen where I post the document there the line items are displayed in a table control & I have to select one of them based on payment term condition. By making changes in configuration payment term field is comming on screen.

<b>My question is that how to select the particular line item based on document number & payment term?</b>

Regards,

Dilip