Mine

function agenda_access($op, $node) {
  global $user;
	
  if ($op == 'create') {
	  return user_access('create agenda');
  }
    else if ($op == 'view') {
 	 return user_access('access content');
  }
  else if ($op == 'update' ||  $op == 'delete') {
	if($user->uid == $node->uid || user_access('edit agenda')) {
	   		return true;
	}
	else {
		return false;
	}
  }
  else {
  	return false;
  }
}