I can't believe I typed that. I really thought that macro features kinda already did that. But they don't. At least, not the ones that are set to always be at the end of the feature tree. Quite often, when you hit the "rebuild" button, the macro feature just sits there doing nothing.
Seems they run with every Ctrl-Q, but otherwise it seems to me they only run if you've made a change that modifies solid geometry. Just editing a sketch won't do it unless some solid changes.
Does anyone know how to make a macro feature run EVERY SINGLE TIME you hit the rebuild button? Well, I mean, other than like writing an addin that watches for you to hit the rebuild button, then looks for the macro feature, reads its code, and executes it...
For reference, here's a macro that inserts just about the simiplest possible macro feature. All the macro feature does is tell you (sans whitespace) that it ran.