Ravenscar vs selective wait

[Simon Wright <simon@pushface.org>]

Is it possible to construct an analog of the selective wait using the
Ravenscar profile?

   Turn_On_The_Lamp;
   Next := Clock + Milliseconds (500);
   select
      accept Reset do
         Next := Clock + Milliseconds (500);
      end Reset;
   or
      delay until Next;
      Turn_Off_The_Lamp;
   end select;

where the Lamp goes off 500 ms after it was turned on, but you can reset
the timer by calling the Reset entry.

Of course, Ravenscar prohibits both task entries and select statements,
so I'm looking for something else! Preferably not involving polling.