Hi Atef,
This is not how the RFQ has been designed. Usually, you are in the need of some items and sends the RFQ to several vendors. Then they can provide a reply for the complete RFQ. If you need to do it based on some items, you can better create a RFQ per group of items for a certain vendor. Or is your process different here? In that case, explain why you need to do it in your way.