// options dialog proc
	INT_PTR CALLBACK Options::ExportOptionsDlgProcS(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) 
	{
		Options* exp;
		if (message == WM_INITDIALOG)
		{
			// record exp instance pointer for subsequent callbacks
			exp = (Options*) lParam;
			SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG)lParam); 
		}
		else
		{
			exp = (Options*)(size_t) GetWindowLongPtr(hWnd, GWLP_USERDATA);
		}
		// hand off to message-handler method
		return exp ? exp->ExportOptionsDlgProc(hWnd, message, wParam, lParam) : false;
	}