How do you specifiy a particlar tape to backup to?

As the title states, I am trying to backup to a particlar tape on a particular day. How would do I go about backing up to a particular tape in a tape drive on a particular day.  For example if I wanted to backup to tape  X on Monday and tape Y on Tuesday how I would I go about doing that.  Once tape X is backed up on Monday it will be pulled and stored for so many days before it it returned to the tape rotation.  I hope my explanation is sufficient, my apologies if it lacks enough information as I am fairly new to Netback and the backup process in general.  Thanks.