Although it's fairly simple once you know what's going on, it's a really complex thing to dive into or explain to someone. Fortunately, there's some good documentation on Oblivion XML. (Unfortunately, I only found that a few weeks ago... I had to learn the hard way.) Since that's for Oblivion XML and not Fallout XML, there have been some additions from what's written there. You can find the new stuff if you browse through master_menu_file.txt, though. You'll also need to learn how to use menu input, which isn't covered there. One way is to detect a hotrect element's <mouseover> value and have your script run IsKeyPressed to detect a click. Another way, which also works for controllers, is to have a custom tag (one with a _ prefix, or user#) that adds the hotrect's <clicked> value and then gets cleared when another value is set via script. You'll find this method used by most interactive menus.