how to retrieve username and password in LDAP using windows Authen

[YRao]

I am going to create intranet application using Windows Authentication
[W2k Active Directory users] using C# asp.net

I am having following problem:

How to retrieve entered username and password in windows Authentication
using LDAP.
Here User name i am getting using
System.Web.HttpContext.Current.User.Identity.Name;
but how to retrieve password?

Because i want filter users based on their 'title' properties in this
situation it will ask entered username and password?

Any suggestion or related code,
any help would be greatly appreciated.

Thanks