PROBLEM IN ATTACHMENT OF ANY WORD FILE IN P.O ( T-CODE- ME22N)

Dear cons

I created a p.o . In this P.o I attached one word file . Then I released the p.o with the help of ME29N.After one week some body has deleted the attachment file & attached another file which was not a appropriate file. Without unreleasing how the system is allowing to change the attachment file.Is there any setting available so that it will not allow to change the attachment file.

nrk