Try to autoclic in the webpage. Only the move works for xpos but not the ypos, there it's using all the time 0. Use this code:
Public Declare Sub Mouse_Event Lib "user32" Alias "mouse_event" (ByVal dwFlags As Long, ByVal dx As Int32, ByVal dy As Int32, ByVal cButtons As Int32, ByVal dwExtraInfo As Long)
Public Const MouseEventF_Leftdown = &H2
Public Const MouseEventF_Leftup = &H4
Public Const MouseEventF_Move = &H8001
Mouse_Event(MouseEventF_Move , Xpos, Ypos, 0&, 0&)
Mouse_Event(MouseEventF_Leftdown , Xpos, Ypos, 0&, 0&)
Mouse_Event(MouseEventF_Leftup , Xpos, Ypos, 0&, 0&)