This macro will toggle Zbrush 4R5’s new dynamic brush setting.
Just install into the Zstartup/Macros/Misc/ folder. From there you can run it in Zbrush under the Macro menu.
You can also assign it a hotkey by pressing CTRL + ALT while clicking on it. Once assigned a hotkey you’ll need to store your hotkeys so Zbrush will startup with the hotkey assignment.