Put the following in your functions.php
:
if (! empty($GLOBALS['pagenow']) && 'post.php' === $GLOBALS['pagenow'])
add_action('admin_footer', 'trash_click_error');
function trash_click_error() {
echo <<<JQUERY
<script>
jQuery(function($) {
$('#delete-action a').unbind();
$('#delete-action a').click(function(event) {
event.preventDefault();
alert('Error!');
setTimeout(
function() {
$('#save-action .spinner').hide();
$('#publish').removeClass('button-primary-disabled');
},
1
);
});
});
</script>
JQUERY;
}