Problem mit IP-Eingabefld

[FriFra]

Ich hab mir von den Schweizern den Code für: "use the IP Address Control in a Form" geholt und eingebaut.
Das Feld erscheint und hat zu Beginn den Focus, so dass ich hinein schreiben kann. Sobald ich aber das Feld verlasse kann ich nicht mehr den Focus darauf setzen (weder mit Tab, noch mit der Maus).

Delphi-Quellcode:

unit frmEasySettings;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, ImgList, ToolWin, StdCtrls, Registry, ShellApi, ExtCtrls;

type
  TForm1 = class(TForm)
    PageControl1: TPageControl;
    TabSheet1: TTabSheet;
    TabSheet2: TTabSheet;
    TabSheet3: TTabSheet;
    ToolBar1: TToolBar;
    ToolButton1: TToolButton;
    ToolButton2: TToolButton;
    ToolButton3: TToolButton;
    ImageList1: TImageList;
    GroupBox1: TGroupBox;
    ComboBox1: TComboBox;
    Label1: TLabel;
    ComboBox2: TComboBox;
    IPAddress: TEdit;
    procedure ToolButton1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure SetIPClick(Sender: TObject);
    procedure ClearIPClick(Sender: TObject);
  private
    FIPAddress: Longint;
    HIPAddress: HWND;
    PrevWndProc: TWndMethod;
    procedure NewWindowProc(var Message: TMessage);
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
uses
  CommCtrl;

const
  IP_ADDRESS_ID: Longword = $0100;

procedure TForm1.ToolButton1Click(Sender: TObject);
begin
  close;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  lpInitCtrls: TInitCommonControlsEx;
begin
  lpInitCtrls.dwSize := SizeOf(TInitCommonControlsEx);
  lpInitCtrls.dwICC := ICC_INTERNET_CLASSES;
  if InitCommonControlsEx(lpInitCtrls) then
  begin
    PrevWndProc := WindowProc;
    WindowProc := NewWindowProc;

    HIPAddress := CreateWindowEx(WS_EX_LEFT, WC_IPADDRESS, nil,
      WS_CHILD + WS_VISIBLE + WS_BORDER + WS_TABSTOP,
      IPAddress.Left, IPAddress.Top, IPAddress.Width, IPAddress.Height,
      Tabsheet1.Handle, IP_ADDRESS_ID, HInstance, nil);
    SendMessage(HIPAddress, IPM_SETFOCUS, 0, 0);
  end;
end;

procedure TForm1.NewWindowProc(var Message: TMessage);
var
  nField: longint;
begin
  case Message.Msg of
    WM_NOTIFY:
      begin
        if PNMHDR(Ptr(Message.lParam)).idFrom = IP_ADDRESS_ID then
        begin
          case PNMIPAddress(ptr(Message.lParam)).hdr.code of
            IPN_FIELDCHANGED:
              begin
                if SendMessage(HIPAddress, IPM_ISBLANK, 0, 0) = 0 then
                  SendMessage(HIPAddress, IPM_GETADDRESS, 0,
                    lParam(LPDWORD(@FIPAddress)));
              end;
          end;
        end;
      end;
    WM_COMMAND:
      begin
        if Message.WParamLo = IP_ADDRESS_ID then
          case Message.WParamHi of
            EN_SETFOCUS:
              begin
                nField := SendMessage(HIPAddress, IPM_GETADDRESS, 0,
                  lParam(LPDWORD(@FIPAddress)));
                if nField = 4 then
                  nField := 0;
                SendMessage(HIPAddress, IPM_SETFOCUS, wParam(nField), 0);
              end;
            EN_KILLFOCUS:
              begin
                if SendMessage(HIPAddress, IPM_ISBLANK, 0, 0) = 0 then
                  SendMessage(HIPAddress, IPM_GETADDRESS, 0,
                    lParam(LPDWORD(@FIPAddress)));
              end;
            EN_CHANGE:
              begin
              end;
          end;
      end;
  end;
  if Assigned(PrevWndProc) then
    PrevWndproc(Message);
end;

procedure TForm1.SetIPClick(Sender: TObject);
begin
  FIPAddress := MAKEIPADDRESS(127, 0, 0, 1);
  SendMessage(HIPAddress, IPM_SETADDRESS, 0, lParam(DWORD(FIPAddress)));
end;

procedure TForm1.ClearIPClick(Sender: TObject);
begin
  SendMessage(HIPAddress, IPM_CLEARADDRESS, 0, 0);
end;

end.