Behavior variable scope

Hello all,

I've downloaded the TGB trial and I'm playing around to see if it is what i need for my project. So far I'm very happy with it but i recently stumbled to a problem that i cant solve on my own. I started learning the basics and by now I'm relatively familiar with all the basic concepts. Today i created a behavior and i attached that behavior to an object that has 1 dynamic field called FuelAmount. There are few functions in my behavior but only built in functions can access it:

function GetFuelBehavior::onUpdate(%this)
{
   %this.owner.schedule(5000, getFuelBehavior.AddFuel());
   echo(%this.owner.FuelAmount);      
   %this.owner.FuelAmount++;
}

function GetFuelBehavior::onPositionTarget(%this)
{
   echo(%this.owner.FuelAmount);      
}

function GetFuelBehavior::AddFuel(%this)
{
   %this.owner.FuelAmount++;
   echo(%this.owner.FuelAmount);      
}

In this example onUpdate and onPositionTarget see %this.owner.FuelAmount without any problems but AddFuel does not. Any custom function i add cant see this dynamic field. I can solve this by using global variables or changing the mechanics but i would like to know what am i doing wrong here. I did search for it on forums a lot but i was not able to find a solution. Any help is appreciated.

Thanks