[flexcoders] Pass Variables and then run a command

[timgerr]

Hey all, I am new with flex, coming from JavaScript and perl.  
I am writing an application that will have lots of MXML components
like a login component, register component and many more.  The problem
is I am trying to have all the components talk to each other, I am
having trouble doing that.  This is my problem, I have a viewStack and
I created a method like this

private var _stackName:String;
private var _stateName:String;
private var _runStackChild:String;

public function ChangeState(stackName:String, stateName:String)void
{
   _stackName = stackName;
   _stateName = stateName;
   _runStackChild = _stackName + ".selectedChild = " + _stateName ;
   _runStackChild;
}

<mx:Button id="btnOne" click="ChangeState('vsTop','register');

So when I click the button the mothod ChangeState is called and passed
are the 2 variables.  At the end ChangeState should run the command 
vsTop.selectedChild = register;

If I clear the method and just add vsTop.selectedChild = register;,
the stack is changed, but when I run _runStackChild; nothing hapends.  

What am I missing???

Thanks,
Timgerr