Thanks Andre,
I Already solved it, and you are right, I'm using "PurchAutoCreate_PurchReq" class and "setPurchTable()" function.
and here is the code I'm using to get the correct value of "VendorRef" from the correct reply.
select _purchRFQTable where _purchRFQTable.RFQCaseId == reqLine.PurchRFQCaseId
&& _purchRFQTable.VendAccount == purchTable.OrderAccount;
select _purchRFQReplyTable where _purchRFQReplyTable.RFQId == _purchRFQTable.RFQId;
purchTable.VendorRef = _purchRFQReplyTable.VendRef;
As for the case of creating one PO from multiple requisitions, it is not our case, but we create multiple POs from one requisition according to each requisition line and its vendor.
Thanks for your support.