DNS Lookup ip to pc name - Dns.GetHostEntry

 Hi,
Im quite new to .net and I need to get the pc name from Ip address , I have code to get ip address from pc name :
 Protected Sub DNSLookup(ByVal IPAddress As String)
        Try
            'performs the DNS lookup
            Dim returnvalue = ""
            Dim he As IPHostEntry = Dns.GetHostEntry(IPAddress)
            Dim ip_addrs As IPAddress() = he.AddressList
            txtIPs.Text = ""
            For Each ip As IPAddress In ip_addrs
             &n ...