Hello Heytem,
If I rephrase your requirement as
I do not want to allow new orders of a particular type created. But I should be able to access old orders.
This can be very easily managed by putting the following code lines in the include ZXWOCU07 of user exit IWO10009.
IF CAUFVD_IMP-AUART = 'PM02'.
MESSAGE 'Sorry ! This Order type has been deactivated.' TYPE 'E' DISPLAY LIKE 'I'.
ENDIF.
With this at the time of Saving the Order of type 'PM02', user will be getting this pop-up and Save will not be possible.
I think you might have to settle for this solution.
Best of Luck
KJogeswaraRao