Can someone give me a little program design advice please?

[Gary Willoughby]

I'm writing a little program in D to perform some database 
operations and have a small question about design.

Part of my program watches a log file for changes and this 
involves code which is wrapped up in a class. So the usage is 
something like this:

auto fileWatcher = new FileWatcher(fileName);
fileWatcher.onChange(delegate);
fileWatcher.start();

Once the start method is called a loop is entered within the 
class and the file is watched. Changes are handle through calling 
the registered delegate. The loop uses different watch methods 
for different platforms.

What i need to be able to do is to stop the current watch and 
change the watched file.

Because this is in an infinite loop, i can't check externally 
i.e. outside of the class, if i need to break from the loop 
simply because control never returns to the caller of the start() 
method.

Am i missing something simple here? Any advice is welcome. I 
thought about threading and message passing but that's maybe 
overkill for something as simple as this?

I've also put this question on stackoverflow here

http://stackoverflow.com/questions/17134809/how-to-check-global-events-inside-an-infinite-loop-within-a-class