This paper describes research involving the use of Java to implement dynamic behavioural control of animated objects. Java ideal for this application because it is an object-oriented language that allows dynamic extension and reconfiguration. The system uses sets of external classes for each actor (called 'evaluators') that modify arrays of parameters passed to them. This provides a flexible method of controlling objects by specifying object data in terms of arrays of numerical values and then using evaluators to modify these. The implementation allows these external classes to be loaded either from a known repository for evaluator classes (the simplest scheme) or by using a 'ClassLoader' to load classes from locations specified at run-time. A search agent can be used to find the classes that match a specification stored in a pre-defined format, and the use of partial matching can yield interesting side-effects on unspecified parameters. The scheme is therefore dynamically re-configurable with the possibility of actors in an animation finding and changing their behaviour over the lifetime of the animation by locating and retrieving new evaluator classes. A test-bed has been developed for the scheme that uses simple VRML geometries controlled by the behaviours.