Wrote a variation of this for different purposes over the past few months. You can get creative and put it in a web service or within your web application. You would also want to send a lot of the initial variables in through ByVal when you call the Function or Method.
Dim user As String = "yourdomain/userToUnlock"
Dim pwd As String = "userToUnlockPW"
Dim de As DirectoryEntry = Nothing
Dim ds As DirectorySearcher = Nothing
Dim url As String = "LDAP://111.11.111.1111/dc=yourdomain,dc=com"
de = New DirectoryEntry(url)
de.Username = "yourdomain/authorizedADuser"
de.Password = "authorizedADuserPW"
de.AuthenticationType = AuthenticationTypes.Secure Or AuthenticationTypes.ServerBind Or AuthenticationTypes.Sealing
ds = New DirectorySearcher(de)
ds.SearchRoot = de
ds.Filter = String.Format("(&(objectClass=user)(objectCategory=person)(sAMAccountName={0}))", user)
ds.PropertiesToLoad.Add("userAccountControl")
Dim result As SearchResult = ds.FindOne
If Not result Is Nothing Then
de = result.GetDirectoryEntry
de.RefreshCache()
de.Properties("LockOutTime").Value = 0
de.Properties("userAccountControl").Value = &H200
de.Invoke("SetOption", New Object() {6, 6})
de.Invoke("SetOption", New Object() {7, 1})
de.Invoke("SetPassword", New Object() {pwd})
de.CommitChanges()
de.Close()
End If
