Measuring interrupted time intervals in Tango

[Jason House]

I'm trying to convert some code that amounts to a busy wait.  I'd like 
to use something very similar to the StopWatch, but I need to let the 
timer keep going.  Typical use is < 1 second.  What's the best way to do 
this with Tango?  I guess one way is to start and stop the stopwatch and 
just add the various results together.  I guess I'm just surprised 
there's no equivalent to boost's timer::elapsedTime()

I could imagine strange uses with ~ 1 minute or more.  What are the 
limits of the StopWatch timing method?