add_filter('gform_pre_render_6', 'populate_customers');
	function populate_customers($form){


	    foreach($form['fields'] as &$field){

		if($field['type'] != 'select' || strpos($field['cssClass'], 'populate-customers') === false)
		    continue;

		$blogusers = get_users('');

		$choices = array(array('text' => 'Search for a Team Member', 'value' => ' '));

		foreach($blogusers as $user) {
		    $choices[] = array('text' => $user->user_email, 'value' => $user->user_email);
		}

		$field['choices'] = $choices;

	    }

	    return $form;
	}