I have a model of a magic portal. It is a circular portal, with a circular frame around it. They are all a part of the same .mdl model.

I am trying to make it so that the portal will slowly rotate, while the frame does not. The frame should stay in place while the portal inside moves in a rotating manner.

Is there a function or method to specify one piece of the model to perform a certain action like rotating, such as by a specific Group or something within the model? For instance, I notice the portal is Group #1 in the .mdl file, while pieces of the frame are other different Group numbers.