I've tested it, they are creating the RFQs with reference to P.R, So I've restricted creation of P.O if the P.R already fully ordered by making message no. 06076 as error message. but on another hand if the RFQ created without reference to P.R there is no standard way to restrict double creation of P.O with this RFQ and it must be done by BADI solution as you mentioned . So my problem is solved .. thanks again for showing me the previous discussion.
