[eluser]Bulk[/eluser]
The built in validation library doesn't support that sort of validation by default no - if you're commited to that way of working you'll have to extend the validation library with something custom - or use callbacks.
But one note, if I'm reading your post correctly - you say you specify the database table to insert data in to as a field in the html? Bad idea. That presents a huge sql injection attack risk, not to mention in general exposing parts of your internal application to the world like that is generally considered bad form.
If I were you I would serious thought to finding a different approach to building your forms - CI gives you many different ways of working in that regard
