DirectoryEntry without using admin user: how to check if account's expired

Hello,
Programming in VS2003-ASP.NET 1.1, I have this problem: Using DirectoryEntry and without any admin user, how can I check if a domain account, that try to login, has expired?
Scenario: User load web application and login using account and password of the Active Directory.
But user account of ActiveDirectory has expired (or password could be expired). For security reason, we don't want to use any account with admin privilegies for connecting through AD. So if user account "jdoe" with password:"jdoe_password" try to login, how to determine if account has expired.
Code:

            Dim Domain As String = "DOMAINXXX"
            Dim sUserName="jdoe": Dim sPassword="jdoe_password"
            Dim myEntry As System.DirectoryServices.DirectoryEntry = New System.DirectoryServices.DirectoryEntry("LDAP://" & Domain, sUserName, sPassword, System.DirectoryServices.AuthenticationTypes.Secure)
            myEntry.Username = sUserName
            myEntry.Password = sPassword

            Dim mySearcher As System.DirectoryServices.DirectorySearcher = New System.DirectoryServices.DirectorySearcher(myEntry)
            Dim myResult As System.DirectoryServices.SearchResult

            mySearcher.Filter = "(&(objectCategory=person)(objectClass=user)(userPrincipalName=" & UserName & "*))"

Dim x as String = myResult.Properties("sAMAccountName")(0)  ''<-- it gets 'jdoe'
Dim y as String = myResult.Properties("userAccountControl")(0) ''<-- it gets Nothing

I don't think it's impossible, or that you have to use an admin user to get that (if you have to use an admin user for connecting to AD, what about security?)
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