Hi,
assuming you have a mailslot configured, you can write a script to run as postexec job. Within this job you can use the command uma to unload the media.
uma -ioctl <SCSIID of Changer> -barcode
When completing the command with uma... < eject.txt and in the eject.txt you need to create before you have something like move S10 M1 and exit at the end. This will ehejct the media.
Of course, you can use omnimm -eject ... as well.
Best regards
Daniel