HI Prasad,
for copy control setting as suggested by prasad,
Go to tcode: VTFL
and the source: LR (return deliv type)
Target : RE (Retrun credit memo)
with item Catg REN
then you try to do return credit memo with ref to ur deliv document
Make sure in tcode VOV8
doc type: RE( return order)
in shipping ->maintained: Delivery type
in billing -> maintained : Billing type
hope this will help you..