Dynamic Deny rule

["Mark Ryan" <markryan@cfl.rr.com>]

I am trying to come up with a iptables rule that will deny ip certain ip
addresses that I can load/unload into a file.
 
To clarify...i run a ftp server and sometimes people screw around and I
want to ban them from logging in.  I need a way to add these ip's into a
'ban list'.  I don't want to add a new rule every time however with a
separate rule for each ip.
 
Is there a way to make a file such as 'banned_ips' and have a rule look
into that file to decide if the ip can log in or not?
 
Thanks,
Mark