Authenticating LDAP users without their input - doable?

[g m]

  I have a critical 'challenge'....
   
  
  It is possible to authenicate on Tomcat using LDAP (Active Directory) 
  (using MS IE browser), but, 'without' the user inputing their username 
  and password - that is, use the cached credentials from user when they 
  logged into the system.
   
  
  I have seen some applications that do this but no idea how.
   
  
  - Is this at all doable ?
  - Do I need a plugin module (or something)?
  - Does IE need to be configured to do this?
   
  
  I am using Tomcat 5.5.9 , Java 1.5, IE 6, Windows XP
   
  Really appreciate a Guru's (or two) opinion/pointer on this one.
  Thanks!


                
---------------------------------
Yahoo! Photos – Showcase holiday pictures in hardcover
 Photo Books. You design it and we’ll bind it!