State handler, receiving value of the selected option

Hi,
while trying to implement state handlers into a new widget I am creating, I gut stuck at the following question: is it possible to change the value of a text field using the text of a selected option of a dropdown-field?

For Example:
I have a select-field which shows all the (custom) posts of a certain type

/* get the custom posts of the type "myposts" */
$my_posts = get_posts(array('post_type'=>'myposts','posts_per_page'=>'-1'));
$my_post_options = array();
$my_post_options[0] = esc_html( 'Please select...');
if ( $my_posts) {
	foreach ( $my_posts as $my_post) {
		$my_post_options[$my_post->ID] = esc_html( $my_post->post_title);  
	}
}

/* later: create the select-field */
'my_custom_post_id' => array(
	'type' => 'select',
	'label' => __('Please select the post:', 'widget-form-fields-text-domain'),
	'state_emitter' => array(
		'callback' => 'select',
		'args' => array( 'my_custom_post_id' )
	),
	'options' => $my_post_options
), 

Now I want to change the value of a text-field depending on the selected option:

'any_textfield' => array(
	'type' => 'text',
	'label' => __('Selected Post to be displayed', 'widget-form-fields-text-domain'),
	'default' => '',
	'state_handler' => array(
		'my_custom_post_id[0]'		=>	array('val', 'input', array('nothing selected yet')),
		'_else[my_custom_post_id]'	=>	array('val', 'input', array(  ???  ) ),
	),
),

is there any way to get the text of the selected option? (I tryed several things like e.g. array(“jQuery(this).val()”) which was obviously not the way to go).