Vista - DirectoryEntry without using admin user: how to check if account'sexpired

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?)
Thanks