Hello Vivek,
Though Aarohi mentioned TECO in the initial post, the requirement is not of TECO. The requirement is: 'To prevent Confirmation after CNF status', let it be TECO or not.
I have seen this preventing (of confirming through fm) is not possible even through the related user-exit CONFPM02. Then only I used the implicit enhancement in the FM itself.
You may suggest accordingly.
Regards
KJogeswaraRao