Using keypress() and keyup() when using an onscreen keyboard - keypress

Question

I have a lovely piece of code which drives a search box on a php page, making the search box dynamic, and it works perfectly. I'm just trying to adapt it, and at a bit of a loss.
At the moment the search must be done on a keyboard to make the search work. This is from the keypress() and keyup() functions within the script.
My problem is that I'm trying to use this search with an onscreen keyboard and no physical keyboard, so there never is a keypress or keyup.
Is there anything I can do do you think to replace these.
Would I be best to add an amended version of the code below (without the keypress/keyup) to each onclick even of my onscreen keyboard, or just amend the code to react to onscreen clicks?
thanks if anyone can help
<!--Javascript to turn keystrokes into search value-->
<script type="text/javascript">
$(document).ready(function () {
// Hide the submit button
$(":submit").hide();
// Bind an event to the keypress in order to override the form submission when pressing the enter key
$("input[name='search_term']").keypress(function (e) {
if (e.which == 13) {
// prevent the form from submitting in the normal manner (return key)
e.preventDefault();
}
});
// Bind an event to the keypress event of the text box
$("input[name='search_term']").keyup(function () {
// Get the search value
var search_value = $(this).val();
// This time we're going to grab data from a file to display
var filename = "functions/search.php";
// Send these values
var posting = $.post(filename, { search_term: search_value });
// Display this value in our results container
posting.done(function (data) {
$("#search_results").empty().append(data);
});
});
});
</script>