How to use multiple "Application-Backup" schedules?

Background: 

    I'm using the (v5.1) NetBackup Oracle Agent.  All of my "Automatic"
    backup schedules have used my one "Default-Application-Backup"
    schedule.  I have noticed that the retention period in the
    *automatic* backup is *not* used for storage. The retention on the
    Application-Backup schedule is always used! 

    I just recently defined a 2nd Application-Backup schedule with a
    longer retention period and now it seems to be always used.  Note:
    Both of my Application-Backup schedules have 24x7 windows.


Question: How do I (is it possible?!) sometimes use the longer retention 
period?  

    For example, my file system backups all do full backups early
    Saturday morning.  Every 4th one of these is for a much longer
    retention than the "normal" ones.  Can I do this with my Oracle
    Agent backups? (I realize that I must tell RMAN to save information
    for at least the longer time).


Thanks for sharing your experience ... I'm fairly new to Oracle Agent usage.

cheers, wayne