My suggestion will be to ensure that data in your VFP view is correct _before_ you try to save it.
That means that you will need to move some of those validations from the backend to the front-end. You can copy some of those rules and have them in both sides (backend and frontend) but then keeping them in synch will be a pain. As far as I know a 3-tier architecture will be a better approach.
Hector Correa