Below is a link to a previous topic about setting up fields that are locked/unlocked with a routine that prompts for a password. If you want it to work differently, post again with more information.
Let's say I have a text field, a dropdown menu and a signature called "Text1", "Drop1" and "Sign1" respectively, and I want them protected with a password in order to fill them, can be a popup window that asks for a password or something like that... I am not really good with JavaScript so I will really appreciate your help
http://forums.adobe.com/message/3314067