i asume you have ever worked with database and dynamic
pagecontent, if you did then just be creative, if you never worked
with that kind of technics then this should need an answer that is
very long, this is really something you should be creative with,
it's the sae pinciple as an newsartice system, and with asigning
id's to banners you can track where te are and wich one and where
to update or delete