Hi Joshua,
I am afraid the "Page selector" field cannot be used as a depending field because it uses JavaScript for selecting/clearing the document, not standard AutoPostback. That is why the only way how you can enforce refresh of the fields list is to click the "Save" button.
The only controls which support your required functionality are Radio button list, TextBox, ListBox, DropDownList, CheckBox list, CheckBox and a few others which are inherited from these ones.