C# Using ActiveDir To Get Names Under A Managers Org Chart?

i am using ODBC to pull data from active directory to get the email for a particular username using the code below.

how can i use AD to pull all the usernames of peolel who report into a prticular manager?

i can transverse the org chart in outlook so im thinking i can do the same using AD...

System.Data.OleDb.OleDbConnection con;
System.Data.OleDb.OleDbCommand cmd;
con = new System.Data.OleDb.OleDbConnection("Provider=ADsDSOObject;dsn=Active Directory Provider");
con.Open();
//Create a command object on this connection
string strSQL = "SELECT mail FROM 'LDAP://DC=amrs,DC=win,DC=ml,dc=COM' WHERE samaccountname = '" + UserName.Replace(@"AMRS", "") + "'";
cmd = new System.Data.OleDb.OleDbCommand(strSQL, con);
try
{
return Convert.ToString ( cmd.ExecuteScalar() );
}
catch (System.Data.OleDb.OleDbException exc)
{
return "ERROR: " + exc.ToString();
}
finally
{
con.Close();
}