Expire a specific file in backup image

Hi,

how can i expire a specific file in backup image using CLI or GUI .. as i know its backup date oct 4 , 2012  and the file name for example: MDR_20120914.tar  ,

 but i  do not want to expire all backup image

master server data:

Symantic Product Name: Symantec Netbackup

Product Version: 7.0.1

Operating System: HP-UX 11iv3