Private Const WM_LBUTTONDOWN As Long = &H201
Private Const WM_LBUTTONUP As Long = &H202
Private Declare Function PostMessage Lib "user32.dll" Alias "PostMessageA" ( _
  ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As _
  Long) As Long
 
Private Function MakeDWord(LoWord As Integer, HiWord As Integer) As Long
   MakeDWord = (HiWord * &H10000) Or (LoWord And &HFFFF&)
End Function
 
Private Sub Command1_Click()
   PostMessage Me.hwnd, WM_LBUTTONDOWN, 0&, ByVal MakeDWord(440, 407)
   PostMessage Me.hwnd, WM_LBUTTONUP, 0&, ByVal MakeDWord(440, 407)
End Sub