ApplescriptObjC: function that is always running?

Question

Hi Community,
As much CPU as it will take up, I need a function that is always running. I tried making a function (called theTest for the sake of the test) that has a repeat block in it and displays some dialog every 3 seconds and then calling on it from the applicationwillfinishlaunching_(aNotification), but the application won't finish launching until the function I call on has finished running (which is never because of the repeat block). Does anyone know how i can make a function that is always running without having any interaction from the user? Or if there is already a function that does that that i don't know about? Thanks. Here's the code I tried:
          on applicationWillFinishLaunching_(aNotification)
                         theTest()
          end applicationWillFinishLaunching_
          on theTest()
       repeat
            repeat with i from 1 to 3
                                                       do shell script "sleep 1"
            end repeat
                                        display dialog "Test"
       end repeat
          end theTest

Answer 1

Ok, so it says this:
textDidChange:
Informs the delegate that the text object has changed its characters or formatting attributes.
- (void)textDidChange:(NSNotification *)aNotification
Discussion
The name of aNotification is NSTextDidChangeNotification.
Availability
Available in Mac OS X v10.0 and later.
Available as part of an informal protocol prior to Mac OS X v10.6.
Declared In
NSText.h
But how do I actually use it (sorry, I'm not too great with ObjC). Would i do something like:
on NSTextDidChangeNotification_(aNotification)
#stuff
end NSTextDidChangeNotification_
Also, how do i specify the text field? Thanks for the help