Advanced condition on a notification

We want a notification to be send only when the ticket is updated by someone else then the person/s on work notes list.

Is this possible to script with an advanced condition?

What I've been trying without success is the following two examples

if (current.work_notes_list != current.sys_updated_by){

  answer = true;

}

OR

if (current.work_notes_list.user_name != current.sys_updated_by){

  answer = true;

}

I always get it to return true even if it's updated by the person who is in the "work notes list" field.