Expanding a form

Expanding a form

Hi all, I am new to javascript and jQuery. I have this simple form that sends collected data to my email:

<form action="mail.php" method="post">
<input name="name" size="25" type="text" />
<textarea name="txt1" rows="5" cols="40"></textarea>
<textarea name="txt2" rows="5" cols="40"></textarea>
<select name="type">
<option value="">---- select ----</option>
<option value="counseling" >Counseling</option>
<option value="training" >Training</option>
<option value="other" >Other</option>
</select>
</form>

Only when the user selects Other in the drop-down list, I'd like another text field to slide down and let him specify what "other" means to him. The new text field content should be sent as well. Should the user change his mind back and select another option, the new text field should slide up. How to get this result?

Any advice would be really appreciated.
Thanks.
Alessandro