$bh_errorMessages=array();

function bh_save_details(){
	global $post, $bh_errorMessages;

	$bh_errorMessages[]="test error";
	$bh_errorMessages[]="another test error";
}

function bh_printErrorMessages(){
	global $bh_errorMessages;
	
	$output='';	
	
	if(!empty($bh_errorMessages)){
		$output='<div class="error">';
		foreach($bh_errorMessages as $msg){
			$output.='<p>'.$msg.'<p>';
		}
		$output.='</div>';
	}
		
	echo $output;
}


add_action('admin_notices', 'bh_printErrorMessages');

add_action('save_post', 'bh_save_details');