stupid ntbackup question

As long as I've worked with Windows servers, I'm embarrassed to admit
that I don't completely understand ntbackup. I've used EMC Retrospect
for many years to back up client computers (including files on a file
server), and I simply relied on SBS Backup when we were running SBS.I
was wondering if someone here could straighten me out.

Here's my confusion. Let's say I have a server running Windows Server
2003. I'm backing up to a bkf file on an external disk. I want to set
up a schedule that does a full backup once a week and a differential
backup every day for the remainder of the week. I also want to store
each backup as a separate file rather than appending, because I don't
want to inadvertently corrupt an entire week's worth of backups due to
some unforeseen problem.

How do I accomplish this? Please note that this is more for my own
curiosity than anything, especially considering that ntbackup will
likely be irrelevant in a few years.

Thanks!
Joseph