Tengo este codigo que tambien sirve para conocer el nombre del host... Es algo largo:
 
Private Const MAX_WSADescription = 256
Private Const MAX_WSASYSStatus = 128
Private Const ERROR_SUCCESS As Long = 0
Private Const WS_VERSION_REQD As Long = &H101
Private Const WS_VERSION_MAJOR As Long = WS_VERSION_REQD \ &H100 And &HFF&
Private Const WS_VERSION_MINOR As Long = WS_VERSION_REQD And &HFF&
Private Const MIN_SOCKETS_REQD As Long = 1
Private Const SOCKET_ERROR As Long = -1
Private Type HOSTENT
   hName As Long
   hAliases As Long
   hAddrType As Integer
   hLen As Integer
   hAddrList As Long
End Type
Private Type WSADATA
   wVersion As Integer
   wHighVersion As Integer
   szDescription(0 To MAX_WSADescription) As Byte
   szSystemStatus(0 To MAX_WSASYSStatus) As Byte
   wMaxSockets As Integer
   wMaxUDPDG As Integer
   dwVendorInfo As Long
End Type
Private Declare Function WSAGetLastError Lib "WSOCK32.DLL" () As Long
Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal wVersionRequired As Long, lpWSADATA As WSADATA) As Long
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
Private Declare Function gethostname Lib "WSOCK32.DLL" (ByVal szHost As String, ByVal dwHostLen As Long) As Long
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal szHost As String) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, ByVal hpvSource As Long, ByVal cbCopy As Long) 
Public Function HiByte(ByVal wParam As Integer)
    HiByte = wParam \ &H100 And &HFF&
End Function 
Public Function LoByte(ByVal wParam As Integer)
    LoByte = wParam And &HFF&
End Function 
Public Function SocketsInitialize() As Boolean
   Dim WSAD As WSADATA
   Dim sLoByte As String
   Dim sHiByte As String
   If WSAStartup(WS_VERSION_REQD, WSAD) <> ERROR_SUCCESS Then
      MsgBox "The 32-bit Windows Socket is not responding."
      SocketsInitialize = False
      Exit Function
   End If
   If WSAD.wMaxSockets < MIN_SOCKETS_REQD Then
        MsgBox "This application requires a minimum of " & _
        " CStr(MIN_SOCKETS_REQD) & ` supported sockets."
        SocketsInitialize = False
        Exit Function
    End If
   If LoByte(WSAD.wVersion) < WS_VERSION_MAJOR Or _
     (LoByte(WSAD.wVersion) = WS_VERSION_MAJOR And _
      HiByte(WSAD.wVersion) < WS_VERSION_MINOR) Then
      sHiByte = CStr(HiByte(WSAD.wVersion))
      sLoByte = CStr(LoByte(WSAD.wVersion))
      MsgBox "Sockets version " & sLoByte & "." & sHiByte & _
      " is not supported by 32-bit Windows Sockets."
      SocketsInitialize = False
      Exit Function
   End If
   SocketsInitialize = True
End Function 
Public Sub SocketsCleanup()
    If WSACleanup() <> ERROR_SUCCESS Then
        MsgBox "Socket error occurred in Cleanup."
    End If
End Sub 
Public Function GetIPAddress() As String
Dim sHostName As String * 256
Dim lpHost As Long
Dim HOST As HOSTENT
Dim dwIPAddr As Long
Dim tmpIPAddr() As Byte
Dim i As Integer
Dim sIPAddr As String
If Not SocketsInitialize() Then
   GetIPAddress = ""
   Exit Function
End If
 If gethostname(sHostName, 256) = SOCKET_ERROR Then
    GetIPAddress = ""
    MsgBox "Windows Sockets error " & Str$(WSAGetLastError()) & _
    " has occurred. Unable to successfully get Host Name."
    SocketsCleanup
    Exit Function
 End If
 sHostName = Trim$(sHostName)
 lpHost = gethostbyname(sHostName) 
 If lpHost = 0 Then
    GetIPAddress = ""
    MsgBox "Windows Sockets are not responding. " & _
    "Unable to successfully get Host Name."
    SocketsCleanup
    Exit Function
 End If
 CopyMemory HOST, lpHost, Len(HOST)
 CopyMemory dwIPAddr, HOST.hAddrList, 4
 ReDim tmpIPAddr(1 To HOST.hLen)
 CopyMemory tmpIPAddr(1), dwIPAddr, HOST.hLen
 For i = 1 To HOST.hLen
    sIPAddr = sIPAddr & tmpIPAddr(i) & "."
 Next
 GetIPAddress = Mid$(sIPAddr, 1, Len(sIPAddr) - 1)
 SocketsCleanup 
End Function 
Private Sub Form_Load()
Text1.Text = GetIPAddress
End Sub 
Espero que te sirva... Cualquier cosa me avisas...