If the low beams are on, the fog lts will stay on. You can test this by pulling the turn indicater/high beam switch towards you until the high beams are on and the low beams are STILL on -- the fog lights will be on also.
So, if you install a "brite box" to use high beams and low beams at the same time, you'll be able to turn your fog lts on also. But, you have to accept the downside of greater wear and earlier failure of your electronic components -- wiring, fuses, bulbs, switches, etc.