I think you have a few hours before it starts breaking down, in taste and effectiveness, especially considering the acidity of OJ. If you have a fridge at work, you could do what I do:
Cheap plastic bowls (Glad or Ziploc, etc).
Pitcher to mix the drink in.
Assemble the components in different bowls and take them to work.
I leave the blender, pitcher, and protein in my desk, but you could find a place for them or even keep them in your car if you had too. I also have a few bags of frozen fruit in our work fridge. When you want one, it is as simple as dumping it all together and running the mixer in it for a minute or so. Just rinse the thing off when you are done and you are good to go. Just make sure to rinse the pitcher as soon as you finish it or the drink turns into cement and is a bitch to clean out (soak it in hot water for 30 minutes).
Here is a shot of the mixer... you can get it at Costco for about $20.