Calling a function that does not exist via reflection/javassist

i need to call a function - (getters and setters of a property), but my problem is, the name of the property is generated at runtime (name of some variable + number).

Is it possible to manipulate the bytecode via javassist or gclib so that the function calls are directed to some proxy object/function, and there the real method name and the number extracted from the called function name, so that i can call the function afterwards (with the number as parameter)?

I tried the following, but it didnt work:

MethodHandler handler = new MethodHandler() {
        @Override
        public Object invoke(Object self, Method thisMethod, Method proceed, Object[] args) {
             String realMethodName=thisMethod.substring(0,5);
             Integer param=Integer.parseInt(thisMethod.substring(5));
            Method m = self.getClass().getMethod(realMethodName);
            m.invoke(self,param);
            return null;
        }
    };