Hi,
There is no standard configuration to achieve this requirement. You can do with BADI ME_PROCESS_PO_CUST
I think You can control on in t-code ME29N,
ME_PROCESS_PO_CUST with interface open. check below link
http://scn.sap.com/thread/1738108
https://scn.sap.com/thread/734053
Call t-code in ME29N. But with out entering delivery date you can't save it in ME21n. So the date will be change at the time of releasing in ME29N.