This would require a bit of electrician know-how. As long as you have access to your attic or space above the ceiling you should be ok. The problem is configuring a switch into the circuit. This process can be easy if you know to trace the wire from the fixture operated by the switch and splice it in, put in a box on the rafter (cut a hole in the ceiling), and wire nut the wires. Next thing would be to wire the MH Fixture to the new box and hang the light.
If you want a seperate switch you have several different options. This would require fishing 2 sets of wire through a hole drilled into the header, secure a box for a switch, pull both wires through. One set will go on one side of the box and the other set will go on the other side. You will then need to splice the "incoming" wire for the switch to a "hot" lead, (preferrably one on a seperate circuit but we cant have everything) which requires shutting the power off to your house or the circuit to that room unless you like to live dangerously, and then using the second set of wires running put in a box on the rafter (cut a hole in the ceiling), and wire nut the wires. Next thing would be to wire the MH Fixture to the new box and hang the light.
Did you get it?
; -)