Hi,
Yes it is true that you have to consider COR6N transaction also for validation.
You can use BAdi WORKORDER_GOODSMVT, method GM_SCREEN_OKCODE_CHECK.
Also you can do this by transaction variant for transaction COR6N using SHD0 transaction.
Below are exits which you can utilize for your enhancement of COR6N transaction also.
Check with the help from ABAP consultant for the same.
CONF0001 Enhancements in order confirmation
CONFPI01 Process order conf.: Calculate cust.specific default va
CONFPI02 Process order confirmation: Customer spec. input checks
CONFPI03 Process order conf.: Cust. spec. check after op. select
CONFPI04 Process order conf.: Customer specific input checks 2
CONFPI05 Process order conf.: Cust. spec. enhancements when savi
CONFPI06 Process order confirmation: Actual data transfer
CONFPP02 PP order conf.: Customer specific input checks 1
CONFPP03 PP order conf.: Cust. specific check after op. selectio
CONFPP04 PP order conf.: Customer specific input checks 2
CONFPP05 PP order conf.: Customer specific enhancements when sav
CONFPP06 PP Order Confirmations: Actual Data Transfer
Regards,
Naresh