Accessing to all instances of a class

[José Antonio Caminero Granja <JCamGra teleline es>]

Hello people,
        How can I access to ALL instances of a class?. I think this is possible
because when style is changed in Control-Center all widgets chage their
appearance. If this is not possible I have to use a list into the class
structure where save a reference to each instance.

Thanks in advance.

-- 
José Antonio Caminero Granja
Valladolid, España