How long on average does it take from submitting an application to the court to have an order varied/changed to the other party receiving the invite to attend court for it to happen.
If it is urgent enough the Order should be applied for ex parte with a date then set for the other party to attend and argue the toss should they wish. On Notice applications vary a lot dependent on whether or not they can be served with the papers, how far away they are etc usually no more than a week or so