Redesign interface for existing form

I need to redesign my form in [login to view URL] (registration required on [login to view URL] to see the form) The form fields change according to user's choices. The changes are not in structure or flow, just the way it's designed. I want the form to be divided into 5 parts, with next and previous buttons for each part, data passed between steps, and all form data submitted to db in the final submit button. Due to the fact that the form length changes according to the user's input, the "next" button in each step will be clickable only when the user completed that step. There will be 5 steps on the top of the screen, and when you finish one you go to the next one: [login to view URL] I will provide the code and the exact fields that are supposed to be in each step.