     public var twoWayCounterpart:Binding;
 
     /**
+     *  @private
+     *  If there is a twoWayCounterpart, hasHadValue is false, and
+     *  isTwoWayPrimary is true, then the twoWayCounterpart will be
+     *  executed first.
+     */
+    public var isTwoWayPrimary:Boolean;
+
+    /**
      *  @private 
      *  True if a wrapped function call does not throw an error.  This is used by
      *  innerExecute() to tell if the srcFunc completed successfully.

            {
                registerDisabledExecute(o);
            }
            return;
        }



        try
        {
            isExecuting = true;
            wrapFunctionCall(this, innerExecute, o);
        }
        catch(error:Error)
        {
            // Certain errors are normal during binding execution, so we swallow them.
            // 1507 - invalid null argument 
            if (error.errorID != 1507) 
                throw error;
        }
