Simply use a Timer to keep changing the cursor position.

Add the following to a form with a Timer.
Code:
Private Declare Function SetCursorPos Lib "user32" (ByVal x As Long, ByVal y As Long) As Long

Private Sub Form_Load()
    Timer1.Interval = 1000
End Sub

Private Sub Timer1_Timer()
    'Move the Cursor in random places
    Randomize
    SetCursorPos Int(Rnd * 200) + 1, Int(Rnd * 200) + 1
End Sub