How difficult is it to develop a script similar to the "quick find" box?
Fairly easy. Take the standard
getitemsandparent query, and add a custom filter to it. Something like this:
<?php
$date='2010-04-14'; // Note the YYYY-MM-DD format
$values=array('filterquery' => '', 'extravarsfilterquery' => '');
$values['childfilterquery'] = " WHERE its.`dateCompleted`='$date' ";
$maintable=query('getitemsandparent', $values);
?>
<table class='datatable sortable'>
<?php require 'displayItems.inc.php'; ?>
</table>
HTH,
Andrew