For an Uno and the likes, you need your VB application to read the serial port and if certain data is received you can move the control. Your Uno can e.g. send "up", the VB app received it, sees that it's "up" and can then move the control up. With a second button, you can e.g. send "down"
If you use e.g. a Leonardo or Micro, it can act like a mouse.