How to put DLL-Forms as Parent to a MainForm-PageControl-TabSheet?

I know, there are a lot of samples from DLLs, but I don't found any one describing how to load DLLs with Forms into a Main form with a PageControl. Each DLL opens an own TTabSheet! Isn't it nice to see how it works?

====The DLL No. 1: =====(make so much you want like this)=========

unit uDLL;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
type
  TDLLForm = class(TForm)
    Label1: TLabel;
    Edit1: TEdit;
    ComboBox1: TComboBox;
    ListBox1: TListBox;
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;
  function Initialisation:HWND; stdcall; forward;
  function CloseDLL:Boolean; stdcall; forward;
var
  DLLForm: TDLLForm;
implementation
{$R *.DFM}
function Initialisation:HWND;
begin
  DLLForm:=TDLLForm.Create(nil);
  DLLForm.Caption:='TestDLL';
  result:=DLLForm.Handle;
end;
function CloseDLL:Boolean;
begin
  DLLForm.Release;
  result:=true;
end;
end.
===========The EXE ========================================

unit uMain;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ComCtrls, StdCtrls, ExtCtrls;
type
  TInitialisation = function:HWND;
  TCloseDLL=function:Boolean;
  TTab = class(TTabSheet)
  private
    CloseDLL:TCloseDLL;
    LibDLL:THandle;
    WinHandle:HWND;
  end;
  TForm1 = class(TForm)
    PageControl1: TPageControl;
    Panel1: TPanel;
    BtnSearchDLL: TButton;
    BtnClose: TButton;
    procedure BtnSearchDLLClick(Sender: TObject);
    procedure BtnCloseClick(Sender: TObject);
  private
    procedure adviceDLL(Name:String);
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.adviceDLL(Name:String);
var
  hndDLLHandle: THandle;
  Initialisation:TInitialisation;
  CloseDLL:TCloseDLL;
  Tab:TTab;
  WinHndl:HWND;
  WinName: Array [0..255] of char;
begin
  try
    // load dll in dinamic type(mode)
    hndDLLHandle := loadLibrary(PChar(Name));
    if hndDLLHandle <> 0 then begin
      // get function address
      @Initialisation:=getProcAddress(hndDLLHandle,'Initialisation');
      @CloseDLL:=getProcAddress(hndDLLHandle,'CloseDLL');
      // if function address exists
      if (addr(Initialisation)<>nil) AND (addr(CloseDLL)<>nil) then begin
        Tab:=TTab.Create(nil);
        Tab.PageControl:=PageControl1;
        WinHndl:=Initialisation;
        Windows.SetParent(WinHndl,Tab.handle);
        windows.ShowWindow(WinHndl,SW_SHOWMAXIMIZED);
        GetWindowText(WinHndl,WinName,255);
        Tab.Caption:=WinName;
        Tab.CloseDLL:=CloseDLL;
        Tab.LibDLL:=hndDLLHandle;
        Tab.WinHandle:=WinHndl;
      end;
    end;
  except
    on E:Exception do ShowMessage(E.Message);
  end;
end;
procedure TForm1.BtnSearchDLLClick(Sender: TObject);
var
  sr: TSearchRec;
begin
  if FindFirst('Test*.DLL',faAnyFile,sr) = 0 then begin
    adviceDLL(sr.Name);
    while FindNext(sr) = 0 do adviceDLL(sr.Name);
    FindClose(sr);
  end;
end;
procedure TForm1.BtnCloseClick(Sender: TObject);
var
  Tab:TTab;
  CloseDLL:TCloseDLL;
begin
  while PageControl1.PageCount<>0 do begin
    Tab:=TTab(PageControl1.Pages[0]);
    CloseDLL:=Tab.CloseDLL;
    Tab.PageControl:=nil;
    Tab.Free;
    CloseDLL;
  end;
end;
end.