bemcli question

I have a backup job for an evault server that creates > 20 backup sets (dbs, vault partitions, indexes).

I would to mark all of the most recent full backup sets as "retain".  I can obviously right click each and set retain.  But I would like to script this for future use, and to reverse the action.  I would also like to be able to check if the backup sets are still resident on disk.  Some of them are past the expiration and I cant seem to find a way to verify if they have been overwritten or not.