The low beam and high beam light section is not individually adjustable. The light housing is one piece, so when you adjust one lower, the other is affected equally. Vehicles with a fog light built into the headlight housing use a projector assembly thats on its own sealed section.
You're better off getting fog lights and installing them in the front bumper opening. Using high beams as fogs will blind and annoy other drivers. I'm sure you've driven in front of someone with their high beams blaring into your rear view mirrors or had a vehicle come from the opposite direction and had their high beams blind you for a second. Why would you want to do the same?