How to delete used code groups in CS notification in Quality management

Dear Experts,

I am trying to delete some previously used codes in CS code group in QS41 transaction code, As per my requirement those codes are not required i want to delete nearly 70 codes in CS code group, but at the time of deletion it is giving error as

"Code 0001 is being used and cannot be deleted

Message no. Q3221"

i tried to convince my user but he is not agreed to keep those codes, he want's to delete the entire codes list and create new codes,so is there any other possibility please guide me, if i maintain deletion flag for that code group (CS) level how it'll effect please guide me

Thanks in Advance,

Krishna.