[Pharo-dev] How to add a trait to a class from an external package?

I have a TCXTBSButton trait that I want to add to a couple of WA classes. Now, I do not want to touch the WA classes as it would mean that I have to maintain them on my own, which isn't good. So, how do I add a trait to a class without changing its code? Programmatically adding a trait to a class on package/configuration load. For methods, I can do a *myownpackage so that things will be saved there. But for traits, I do not know how. Help :-) Phil