Setting up a dynamic form.

We are trying to create a "Contact Us" page that will provide a contact form based on the user's selection of a category.

Ideally we want the following setup:
1) User will select one of 11 options from a pull-down menu
2) Based on the option selected, one of three forms will appear below
3) User will fill out the form (Username, First Name, Last name, email, etc) and click submit
4) The case will populate in the case system in NS with the fields set up, but also with the category chosen from step 1 as the Case Type.

The problem we are running into is setting up the forms properly so they will submit properly. We have it set right now to have the pulldown appear on the page. We then have 3 <div>s set up for each form with display:none set. When they select an option, it sets the appropriate <div>'s display to 'block' (making it appear). The problem with this is that the other fields (from the invisible forms) are still "there" when you try to submit, so it creates a huge error.