Export on behalf of customer's customer

Respected Sir, We (Party One) are in receipt of an order from our customer (Party two) in india who inturn got an order from overseas buyer (Party Three). And overseas buyer has to sell it to end customer(Party four). Our customer is asking us to issue Proforma invoice where we have to mention ourselves as exporter along with "On behalf of name of our customer's Customer". Can we mention "On behalf of" "name of customer's customer" in our Proforma Invoice.Please advice