After you've created your view to display the data that you want, now it's time to add your argument. Go to the argument box on your view and add the nodereference cck field that you'd like to act as the primary argument for your block. Once you've done that on the settings for that field select "Provide default argument," then under your settings for that select "Node ID from URL." Now, my first thought was, "but what if my Node ID isn't in my URL?" Well, it's actually a lot smarter than that and just goes based on the Node ID whether it's in the URL or not. Since we're using a block the only arguments are coming from which Node ID you are accessing.