How to make a fla****ng light?

In my ongoing attempt to learn Cocoa my next wee project is going to be a
'is the internet up?' type app. Basically it will send a single ping
packet
to three addresses once every n-seconds (say 120) and *****s the results.

That part isn't a problem.

As part of the results I want a graphic of a fla****ng LED. Red for
'Internet
is down', green for 'Internet is up'. My question is this: how do I make
it
flash? The method I'm considering is to have an NSTimer that fires every 2
seconds and calls a method that toggles the graphic between whatever two
of
the three graphics are appropriate - RedLED on, GreenLED on, LED off.

Or is there a better way?

Many thanks.

Jim
-- 
http://www.ursaMinorBeta.co.uk
"When one of the local cats, an especially fluffy creature with a vast
tail, rushed down the street towards me the other day, mewing delightedly,
I have to admit it was probably shouting 'HAZ CHEZBURGR?' " - Bella, ucsm