Up through Creo 7 there is no built-in function that supports scaling of bodies or surfaces independently in part mode. The scale model function applies to all dimensions in the part, so it is global. I am pretty sure this has not changed in Creo 8 or 9.
In Pro/Mold extension there is a different "shrinkage" feature available, it can be selectively applied based on feature history but not by body or feature.
The only practical way I can think of to do this would be to create a selection query that could pick all dimensions of a body or feature and then create relations for them such that you could scale them using a scalar multiplier in a relation for each dimension.
I have used Notebooks (.lay files) to selectively scale features within a model but this gets rather convoluted.
