Change not done in the user fields of operation for production order save

Hi Experts

I need to change the user fields of the operation like (SLWID and USR00 )for a production order at the time of save.

So am using the exit PPCO0001 and using the OPERATION_TABLE internal table in the exit to chang the details.

I have done coding in the exit to change SLWID and USR00 in OPERATION_TABLE internal table, but its not updated in the database and the screen also. I dont understand why.

Please let me know, why the update are not happening.

Thanks in advance.

Regards

Rajaram