You want the save_post hook
https://codex.wordpress.org/Plugin_API/Action_Reference/save_post

add_action( 'save_post', 'my_save_post', 11, 2 );

function my_save_post($post_id, $post){

   //if it is just a revision don't worry about it
   if (wp_is_post_revision($post_id))
      return false;

   //if the post is an auto-draft we don't want to do anything either
   if($post->post_status != 'auto-draft' ){

      // unhook this function so it doesn't loop infinitely
      remove_action('save_post', 'my_save_post' );

      //this is where it happens -- update the post and change the post_name/slug to whatever you want
      wp_update_post(array('ID' => $post_id, 'post_name' => YOUR_SLUG_HERE );

      //re-hook this function
      add_action('save_post', 'my_save_post' );
   }
}

I’ve only started playing with it so there may be other ways, but you can create a grouped field and repeat that, which is much the same as the way ACF does things

piklist('field', array(
    'type' 			=> 'group'
    ,'label' 			=> 'Event'
    ,'add_more' 		=> true
    ,'fields' 			=> array(
	  // add the fields that describe an event
          array(
             'type' 			=> 'text'
             ,'field' 			=> 'event_name'
             ,'label' 			=> 'Event Name'
          )
         // ... etc - more fields
    )
  ));

Sorry to resurrect on an old thread from 2013 but was this ever implemented? The docs are missing for this field. I had a look through the demo code and couldn’t see mention of it.