[jQuery] Dynamic form field changes aren't POSTed

[Slantedview]

I'm using JQuery to, among other things, dynamically create and modify
form input elements in response to events. I've noticed though, that
whenever I do this, any newly created inputs or changes to existing
inputs don't make it through when the form is POSTed. Example:

$(function(){
        $("#someButton").click(function() {
                fieldCount = parseInt($("#fieldCount").val());
                $("#fieldCount").val(fieldCount + 1);
                .........

I can see the value of my fieldCount field changing when #someButton
is clicked, but when I submit the form, the value is what it was
originally.

Am I missing something?