Hiding a multiselect field on load

I want to design a form that shows a single field on load. In this case, it would be a dropdown list of subject areas. Once a user has selected the subject area, the remainder of the fields pertaining to that subject area would be shown. I can accomplish this, except for the multiselect fields, which apparently cannot be hidden on load. Being able to hide the multiselect fields on load is critical to my attempt to create a user-friendly form. Can something be done to allow multiselect forms to be hidden on load and then shown upon user action?

Thank you.

K Henderson