JQuery :: Change Function - Adding Class To All Of Inputs

I have a form that is initially submitted by normal submit button, but after that I want it to resubmit on change(). I thought I'd be able to pick up the secondary change()s by adding a class to all of the inputs. However I now understand that won't work by default because the change() can't be attached to the class added by the the submit() as it didn't exist at the time, it was added by Jquery. I've since discovered on() but I'm now stuck on where to include it.

Here's the script so far:
The submit() adds the 'stu' class, and then the change() tries to select it but can't
<script>
$(document).ready( function(){
$("#search_choices").submit( function(evt){
runSearch();
$("input").addClass("stu");
evt.preventDefault();
});
});
$('.stu').change( function(){
runSearch();
});

function runSearch(){
var sFor
= $("#for").val(),
sWhere
= $('input[name=where]:radio:checked').val();
$("#search_results").load('search.php', { where: sWhere, treb: sFor } );
};
</script>