Use this screen to change your mouse configuration in the virtual machine:
In the panel Mouse:
Host mouse type — Select one of the supported types from the drop-down menu, or choose autodetect to automatically detect the type of mouse you are using.
In the panel Connection:
autodetect — Automatically detects the device file for your mouse.
specify the host device — Select this option, then use one of the choices in the drop-down menu to specify a mouse device. Use /dev/mouse for serial mice and /dev/input/mouse for USB mice. To use an alternate device file, type the name of a device file in the text box.