Related custom attributes

I understand how to add custom attributes (and enumerations) to a work item. What I want to do is have custom attributes that are inter-related.

For example, say I have an "animal" field (dog, cat, hippopotamus etc) and a "breed" field on my work item. When entering a work item, the originator selects a type of animal and the "breed" list automatically filters to only allow breeds appropriate to that animal.

Is there a way to do this in RTC ?