123

...

case WM_COMMAND:

        if ((HWND)lParam == hButton_get_data)
        {

            WNDCLASS w;
            memset(&w, 0, sizeof(WNDCLASS));
            w.lpfnWndProc = ChildProc;
            w.hInstance = hInst;
            w.lpszClassName = "ChildWClass";

            RegisterClass(&w);

            child = CreateWindowEx(
                0,                              // Optional window styles.
                "some class",                     // Window class
                "child",    // Window text
                WS_CHILD | WS_BORDER | WS_VISIBLE,            // Window style
                100, 100,
                600, 700,
                hwnd,       // Parent window
                NULL,       // Menu
                hInst,  // Instance handle
                NULL        // Additional application data
            );



            if (!child)
            {
                MessageBox(NULL, "Error", "Error", MB_OK);
                DestroyWindow(hwnd);
                break;
            }

            ShowWindow(child, SW_NORMAL);
            UpdateWindow(child);

        }

...