This is the view inside of the ceiling with the new wire pulled in through the hole in the laminated beam.

This hole going up into the ceiling was made with a Milwaukee 0721-20 V28 28-Volt Lithium-Ion 1/2-Inch Cordless Right Angle Drill

This view is the inside of the wall through the hole in the previous photo.
The big hole in the wall was needed to accommodate the big angle drill and a long auger drill bit.

The existing dimmer switch box had the correct wiring (Hot and neutral) in it to facilitate the connection to another light fixture.
The light fixture hook is attached to the deep octagon electrical box and the access hole in the ceiling is patched.