Sorry for speaking to myself. I have figured it out. I have done the following. Thanks again for your help @elliot
<script type="text/javascript">
jQuery(document).on('acf/setup_fields',function(e){
//alert('test');
jQuery( "#dialog" ).dialog();
});
</script>

Hi @elliot,
thank you for your answer. I have already read this article, but I don’t reaklly understand it. Do I have to create the acfg/setup_fields action in my wordpress functions.php or directly into my HTML in the create_field function() ?
My create_field function looks like this now. But it doesn’t work 🙁
function create_field( $field )
{
// defaults?
/*
$field = array_merge($this->defaults, $field);
*/
// perhaps use $field['preview_size'] to alter the markup?
// create Field HTML
?>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css" />
<script>
$(document).live('acf/setup_fields', function(e, div){
// div is the element with new html.
// on first load, this is the $('#poststuff')
// on adding a repeater row, this is the tr
$(div).find('.class').each(function(){
$(this).doIt();
});
});
function doIt() {
alert("Hello World!");
}
</script>
<div id="dialog" title="Basic dialog">
<p>This is the default dialog which is useful for displaying information. The dialog window can be moved, resized and closed with the 'x' icon.</p>
</div>
<?php
}
Cheers,
javanese