case WM_INITDIALOG:
{
    ...

    // Add Status Bar
    HWND hStatus = CreateWindowExW(0, STATUSCLASSNAMEW, nullptr, WS_CHILD | WS_VISIBLE | SBARS_SIZEGRIP,
        0, 0, 0, 0, hWnd,
        reinterpret_cast<HMENU>(IDC_STATUS_BAR), GetModuleHandleW(nullptr), nullptr);

    int status_parts[] = { 100, 160, 300 ,-1 };

    SendMessageW(hStatus, SB_SETPARTS, 2, reinterpret_cast<LPARAM>(&status_parts));
    SendMessageW(hStatus, SB_SETTEXT, 0, reinterpret_cast<LPARAM>(L"Test"));

    return TRUE;
}
case WM_SIZE:
{
    SendMessageW(GetDlgItem(hWnd, IDC_STATUS_BAR), WM_SIZE, 0, 0);
    return TRUE;
}