How Multiple Items are transferd from POWL at portal to Web Dynpro Appl

i am having a POWL at portal where multiple items are listed. user can select single or multiple rows and press a button here. on pressing of button i am opening a web dynpro application in new window using OBN(Object Based Navigation).

now my problem is to transfer multiple items(only Key Field) from POWL to Web Dynpro Application.

any help or link is appriciated.

thanks in advance

Regards