I understand why you possible would need to add fields to your form, it might be better to either have a text area that is hidden that is updated with the data you want to convey to the the server or to have hidden input fields that get updated at time of submission.
Using 'id's' to hook the inputs IMHO is not the way to do this, what would be better is to use the DOM method of referencing and with your form submission you can pass a reference of the form to the function that makes it simpler to access those form elements.
<form action="postaddress.php" method="post" onsubmit="return validate(this);" />
<input name="one" type="hidden" value="">
<input name="two" type="hidden" value="">
<input name="user" type="text" value="">
<input name="email" type="text" value="">
<input name="submit" type="submit" value="Submit">
Where it says onsubmit="return validate(this);" the function called validate(this) is having the form object passed to it via the 'this' object that refers directly to the form.
o.one.value = new Date().getTime(); // get a time stamp
o.two.value = md5( o.user.value + " " + o.email.value );
So... when you access the object 'o' in the validate function, you can hook the form fields you want to access more quicker. The example is overly simple but you should get the idea on how to move on.