Mass change asset class

We have all of our desktop and laptop computers in one asset class that has 5 years depreciation. We now have a need to depreciate all laptop computers over 4 years, so we would like to move laptops from the current class (5 year depr) to a new class set up for 4 year depreciation. I had hoped to mass change asset class using substitution, but class is not a field that can be changed using that method. Is there a way to accomplish this without creating new asset numbers? I've seen reference to transaction ABUMN but I'm not sure if this is what I should use to do a mass change.