Change the DPI dynamically for mouse usage

I know in Windows it is possible to change mouse speed. However, I am wondering is it possible to this dynamically. For example, those moments you just need to move the mouse pointer a little, I find are very difficult due to some RSI problems. If I could hold down a key and then dynamically change the mouse speed it would be a lot easier. Thanks

Question by dublintech on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.