Its not possible, because that would be a bot. That is, if you mean a macro to let you keep crafting when you are afk. If you mean instead of hitting "repeat", that seams a lil silly to me. In the time it takes you to hit a macro, you can just click "Repeat". Doesnt seam like that much of a shortcut to me. I doubt that SOE is going to make any provisions for this, as that would make the lives of craft-bot coders much, much easier.