There are only two options: Restart Now/Restart Later. "Restart Later" meaning that it will ask you again in 10 minutes. So, if you're willing to work for the next 4 hours before rebooting, you'll need to answer this question 24 times.
I think the worst aspect of this dialog though, it is that it steals the focus.
So, to get rid of it:
Start / Run / gpedit.msc / Local Computer Policy / Computer Configuration / Administrative Templates / Windows Components / Windows Update / Re-prompt for restart with scheduled installations
You can configure how often it will bug you (I initially re-configured it for 720 minutes, which means I'll be asked twice on a work day), but have since decided to completely disable it.
This setting is only loaded when Windows starts, so a reboot is required. If that dialog is on your screen now, just stop the "Automatic Updates" service (but keep it as Automatic, so it gets reloaded on the next start) and you won't see it again.
Or, if you don't want to reboot, just do :
Start / Run / gpupdate.exe /force