Looping Through Active Directory To Get Managers And Direct Reports?

I've got an intranet based reporting tool (VB.Net + ASP.Net Integrated Windows Authentication) that looks up users and managers from a SQL Server 2005 table to roll up the reporting to manager level. This table is currently manually maintained and I've been asked to make it more dynamic as it is going to be up-scaled for far more users. Therefore I'm looking to link in with the Active Directory to create an Org table in the back end which will replace the current manually entered one.I'm comfortable getting user data from the AD, but not so sure as to the best approach to set this up, I was thinking of the following table:

CREATE TABLE dbo.Employees
(
EmpID nvarchar(8) PRIMARY KEY,
EmpName nvarchar(30),

[code]...

EmpID will be the NetworkID (sAMAccountName).Then this will need populating from the AD, I'm guessing through recursive calls to fill in the fields. I'm then not sure how to structure the code so that it will capture every employee under every manager starting at a given level. I'm currently using the below to capture the direct reports for a given manager:

Public Function GetDirectReports(ByVal ADFullName As String) As ArrayList
Dim adItems As ArrayList = New ArrayList
Dim rootEntry As New DirectoryEntry("LDAP://" & ADFullName)

[code]...