How do I create an event handler to check that a class has completed its tasks
before I continue with my next line of code? For example, in the code below,
the class that is being used must hit a database before it is able to return a
value for myVar. However, the trace statement executes before the value of
myVar has been changed.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
creationComplete='init()'>
<mx:Script>
<![CDATA[

public function init():void{
var something:TestClass=new TestClass
trace("here="+something.myVar)
}

]]>
</mx:Script>
</mx:Application>

If you are loading from a database you have a listener function on the result,
something like onResult(event:ResultEvent)
In that listener function you usually parse the data and then dispatch a
(custom) event that the data has loaded. Any object that needs to know about
this event, registers for the event and in a listener function you can proceed
with your code.