restrict permission to user of default menu tab

Hi,

Please, how do I restrict a 'default menu tab' to the user (owner of user page). I have moved buddylist as a tab to user pages, and well know everyone can see another person's buddylist, requests, etc.

So just more clearly, when I select 'default menu tab' for a view, how can it make visible only to the user looking at their own user page?

Is it an argument? ... as have tried :

global $user;
// Make the first argument the uid of the current user if not already set
if(arg(0) == "user" && is_numeric(arg(1))){
  $args[0] = arg(1);
}else{
  $args[0] = $user->uid;
}

to no avail.

Would most appreciate any help, and thank you.
Lilian