Here is the code. I use this strategy for dynamic assignment of functions to events, like nav items. Enjoy.

Code:
//  inside class containing function targeted by your string...

public function executeThis(myFunctionStringName:String, someID:uint):void {
     var thisSoonToBeFunction:String = myFunctionStringName;
     this[thisSoonToBeFunction](someID);
}
					
public function nameOfMyFunction(someID:uint):void
...