Manoranjan,
Apart from G Lakshmipathi's suggestion (which involves coding), please read Murali's suggestion too (which also involves coding)
http://www.sapfans.com/forums/viewtopic.php?f=5&t=122374
In Murali's suggestion, he suggests to check the copying requirement routine at item level, but I would suggest you to check field copying requirement at header level (F2>RE).