Temporarily slow down мышь by прессинг shift key

sometimes high точность while using мышь is needed, e.g. when resizing windows, cropping images. It would be very convenient to have some sort of мышь speed modifier key which while pressed down would slow the мышь down. Windows гve seen some laptops running having touch pad контроль панель where you хан set various modifier keys for мышь speed, горизонтальный / вертикальный / диагональный movement, и т.д. Бут I want to achieve this on Ubuntu 14.10 or higher using external мышь.

Thanks!