If a certain option value is selected, open a required input

If a certain option value is selected, open a required input

Hi!

Here is my problem -

I have a standard form that uses jquery to validate. It works great, and I love it. However, I am needing to ask the user for their address ONLY if they select one of the four option values in the drop down box. I was wondering how I would get the box to slide down when that certain option is selected?

I would ask everyone for their address, but I don't think it should be required to contact me, so therefore I would only like it when this certain option is selected.

Here is my code for the drop down:


            <label for=subject accesskey=S>Subject:</label>
            <select name="subject" type="text" id="subject">
              <option value="Inquiry">General Inquiry</option>
              <option value="Attending a Seminar">Attending a Seminar</option>
              <option value="Begin investing with xxcompany name herexx">Invest with ETFs</option>
              <option value="Media">Media Inquiry</option>
            </select>


I need to ask the user for their address when the "attending a seminar" option is selected.

Thank you so much![/code]