You can also use jQuery to trigger additional fields to display when one is selected, e.g. form field A gets a value entered by the user, and once that happens fields B and C are displayed.
You can use jQuery's $(document).ready() method to add an onchange event to a form field.
Select it per the example above and chain a .change() method to it that defines a function to select and .show() the additional form fields. You may want to use CSS or jQuery in the .ready() function to add display: none; to the fields to be shown. Anything can be done with a CCK form, you just need to know the IDs of the divs created for the form fields.
Pseudo-example:
$(document).ready(
function() {
$('#form-field-a').change(
function() {
$('#form-div-b').show();
$('#form-div-c').show();
}
);
$('#form-div-b').hide(0);
$('#form-div-c').hide(0);
}
);