var b = coreObj.AttachToHWND(hWnd);
hWnd
is a Win32 API window handle.// hwnd is a valid handle of a 'Internet Explorer_Server', 'IEFrame' or 'TabWindowClass' window inside IE.
var hwnd = 0x1C05B8;
var core = new ActiveXObject("Twebst.Core");
var browser = core.AttachToHWND(hwnd);
browser.Navigate("http://www.codecentrix.com/");