...
var
    FEvent: THandle;
    sDocumentCompleteResult: string;

implementation

...

function TParse.GetDocumentInnerHTML(const url: string): string;
      procedure ResultCallback(text: PWideChar);
      begin
         sDocumentCompleteResult := WideCharToString(text);
         SetEvent( FEvent);
      end;
var
  Command: TWebBrowserCommand;
begin
  Command.Number          := CMD_NAVIGATE;
  Command.Parameter       := PChar(url);
  Command.ResultCallback  := @ResultCallback;

//запускаем navigate
  SendCommandToWebBrowser(FWebBrowserContainer1, @Command);

//ждём
  WaitForSingleObject(FEvent, INFINITE);// вместо INFINITE можно вставить интервал времени ожидания, на случай зависания - timeout

  result := sDocumentCompleteResult;
  CloseHandle(FEvent);
end;

    FEvent := CreateEvent(nil, false, false, nil);
    pagecontent := GetDocumentInnerHTML(url);

  Command.Parameter :=   Command.Parameter := PAnsiChar(AnsiString(sURL));

Container^.WebBrowser.Silent := True;

function MsgOnlyWindowProc(hwnd: HWND; uMsg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
var
  Container: PWebBrowserContainer;
  Command: PWebBrowserCommand;
begin
  case uMsg of
    WM_USER:
    begin
      Container := PWebBrowserContainer(wParam);
      Command   := PWebBrowserCommand(lParam);

      case Command^.Number of
        CMD_NAVIGATE:
        begin
//          Container^.WebBrowser.Silent := True;
          Container^.WebBrowser.Navigate(PAnsiChar(Command^.Parameter), EmptyParam, EmptyParam, EmptyParam, EmptyParam);
          while (Container^.WebBrowser.ReadyState <> READYSTATE_COMPLETE) do
          begin
            Application.ProcessMessages;
            Sleep(1);
          end;
          Command^.ResultCallback(PWideChar((Container^.WebBrowser.Document as IHTMLDocument2).body.outerHTML));
        end;

      end;
    end;
  else
    Result := DefWindowProc(hwnd, uMsg, wParam, lParam);
    Exit;
  end;
  Result := 1;
end;

Container^.WebBrowser.Navigate(WideString(PAnsiChar(Command^.Parameter)), EmptyParam, EmptyParam, EmptyParam, EmptyParam);

          while (Container^.WebBrowser.ReadyState <> READYSTATE_COMPLETE) do
          begin
            Application.ProcessMessages;
            Sleep(1);
          end;