Technically you can get the position of the mouse cursor (provided it's not being held in place, which some games do), and translate that into joystick movement or keyboard keypresses, however that's probably more suited to a dedicated application, rather than a VoiceAttack command.
VoiceAttack can control a virtual (vJoy) joystick using
a plugin, and it can of course press keyboard keys, but you'd need to put together a command that translates mouse movement into either of those (and that moves the cursor back to the center of the screen periodically, so you don't run into screen edges), in a way that produces usable output.
For adequate responsiveness you'd likely have to use the advanced/experimental "Resource balance offset" option.