Well, I was writing a listbox class more to my liking (never liked those list boxes that store their items, and as a consequence, handle the list structure/order which should be left to the client), mouse events would have to be redirected generically to control trees, and I can see myself rewriting the entire Turbine.UI.* API from that point.
As tempting as it might be, I'll just forget about MouseWheel events for the time being, I think
Edit: Or I might try to use a listbox as a master control for my listbox, that might actually work.