ASP.NET w/ VB Getting UserName after isAuthenticated from Active Directory

I have three issues that I am struggling with in my code for authenticating users in AD.

1. I want to pass the Username to the next page so that I can use it in an Audit Trail later on during the users experience with the app.  I do not want to use a query string.  

2. I want to get the users First and Last Name after authenticating.  I have no clue how to do this and no clear explanation on the web has been found.

3. I want the user to be a member a specific group in AD.  I am using LDAP

Can anyone help me thorugh these issues?  I have included my code below - works fine except that any member of the domain can login..not just members of the group

 I am assuming that the majority of the code needs to go here except for the username,etc that will passed off to the next page.

I have this for getting at the specific group but I can not figure out how to use this in my code.  As is - does not work.
LDAP://my.domain.org/CN=OU=ABC Managed Users,OU=Users,OU=MySite,OU=ABC, DC=my,DC=domain,DC=org

imports System
imports System.Web.Security
imports System.Security.Principal
imports System.Web
imports System.DirectoryServices
imports System.DirectoryServices.DirectoryEntry
 
 
 
 
 
Partial Class Authenticate_With_Active_Directory
            Inherits System.Web.UI.Page
 
 
        
            Protected Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
                Dim isAuthenticated As Boolean = AuthenticateUser()
                If isAuthenticated Then
 
                   Dim sScript As String
                   Dim cScript As String
        
 
        sScript = "<SCRIPT Language=JavaScript> newWin = window.location.href='/default.aspx'; </SCRIPT>"
        RegisterStartupScript("NewWindow", sScript)
        cScript = "<script language='javascript'> { window.close() }</script>"           
        
		        
                     
		 Else
                    Incorrect.visible = True
                End If
            End Sub
 
            Private Function ValidateActiveDirectoryLogin(ByVal Domain As String, ByVal Username As String, ByVal Password As String) As Boolean
                Dim Success As Boolean = False
                Dim Entry As New System.DirectoryServices.DirectoryEntry("LDAP://" & Domain, Username, Password)
                Dim Searcher As New System.DirectoryServices.DirectorySearcher(Entry)
                Searcher.SearchScope = DirectoryServices.SearchScope.OneLevel
                Try
     			Dim Results As System.DirectoryServices.SearchResult = Searcher.FindOne
     			Success = Not (Results Is Nothing)
     			Dim aCookie As New HttpCookie("lastVisit")
     			aCookie.Values("userName") = txtUserName.Text
     			aCookie.Values("lastVisit") = DateTime.Now.ToString()
     			aCookie.Expires = DateTime.Now.AddHours(4)
    			 Response.Cookies.Add(aCookie)
		Catch
     			Success = False
		End Try
 
                Return Success
            End Function
 
            Private Function AuthenticateUser() As Boolean
                Dim username As String = txtUsername.Text
                Dim password As String = txtPassword.Text
                Dim domain As String = "my.domain.org"
 
                Dim isAuthenticated As Boolean = ValidateActiveDirectoryLogin(domain, username, password)
 
                Return isAuthenticated
			
            End Function
    
        End Class

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