Going to be hot in my shop

[Sawin]

my townhome is 3 floors on the southern end of a mult-unit building. I have this same issue in the top 2 bedrooms....

step 1. Turn AC to 70ish (I've never gone lower, because the bottom floor will be too cold).
step 2. Close ALL the vents on the lowest floor.
step 3. Strategically close any other vents along the air-path, that leads to the top floor. (my living room has 3 in the row, I closed 1 of them that was closest to the thermostat).
step 4. Direct the air-flow from the vent in your top floor office, away from the wall/windows with one of these (random link of the product, or make one yourself - http://www.qcidirect.com/air-deflector.html)
step 5. Add a small personal desk fan to your workspace.

For me, the above = mission accomplished.

edit - oh, and obviously get some good blinds for the windows to block out some of the sunlight.