Несколько твиков и похоже на работу:
Private Declare Function SetCursorPos Lib "user32" (ByVal x As Int32, ByVal Y As Int32) As Int32
...
With Win
Dim left As Int32 = CInt(.Left + .Width - CURSOR_OFFSET_MEDIUM)
Dim top As Int32 = CInt(.Top + .Height / 2)
SetCursorPos(left, top)
End With