I have a custom content type in Alfresco (3.3 Enterprise, if it matters) and I can assign one or more categories to that content. So far so good.

But can I restrict the set of possible categories to only a subset of all categories? If, for example, categories looked like below, how can I restrict the user to only selecting a region subcategory (e.g. Europe, South America, etc).

Categories
+ Software Document Classification   <- I do not want these to be picked.
|  + Utilisation Documents
|  + Software Descriptions
|  + ...
|
+ Regions                     <- I want to restrict the
|  + Latin America               user to this subset of categories.
|  + Europe
|  + ...
+ ...

Is this possible?