...get the IWebbrowser2 Interface from a Window Handle?

uses
  ActiveX, Shdocvw_tlb, MSHTML_TLB;

type
  TObjectFromLResult = function(LRESULT: lResult; const IID: TIID; wParam: wParam;
    out pObject): HRESULT; 
  stdcall;

function GetIEFromHWND(WHandle: HWND; var IE: IWebbrowser2): HRESULT;
var
  hInst: HWND;
  lRes: Cardinal;
  Msg: Integer;
  pDoc: IHTMLDocument2;
  ObjectFromLresult: TObjectFromLresult;
begin
  hInst := LoadLibrary('Oleacc.dll'); @ObjectFromLresult :=
    GetProcAddress(hInst, 'ObjectFromLresult');
  if @ObjectFromLresult <> nil then 
  begin
    try
      Msg := RegisterWindowMessage('WM_HTML_GETOBJECT');
      SendMessageTimeOut(WHandle, Msg, 0, 0, SMTO_ABORTIFHUNG, 1000, lRes);
      Result := ObjectFromLresult(lRes, IHTMLDocument2, 0, pDoc);
      if Result = S_OK then
        (pDoc.parentWindow as IServiceprovider).QueryService(IWebbrowserApp,
          IWebbrowser2, IE);
    finally
      FreeLibrary(hInst);
    end;
  end;
end;

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