Find out your state laws. Most states require the parent with primary custody to notify of a move at least 30-60 days in advance and then you have the chance to file a court request to try and stop the move.
At the very least you children are not available for the time you are entitled to in your court order so I would talk to an attorney about filing a contempt of court charge and asking for make up time. If he moved further away you could possibly have a case to request a change in custody.
