Usando il codice che hai postato in versione "sfrondata" dalla roba inutile:
codice:
Private Type POINTAPI
x As Long
y As Long
End Type

Private Const MOUSEEVENTF_ABSOLUTE = &H8000 ' absolute move
Private Const MOUSEEVENTF_LEFTDOWN = &H2 ' left button down
Private Const MOUSEEVENTF_LEFTUP = &H4 ' left button up
Private Const MOUSEEVENTF_MOVE = &H1 ' mouse move
Private Const MOUSEEVENTF_MIDDLEDOWN = &H20
Private Const MOUSEEVENTF_MIDDLEUP = &H40
Private Const MOUSEEVENTF_RIGHTDOWN = &H8
Private Const MOUSEEVENTF_RIGHTUP = &H10

Private Declare Sub mouse_event Lib "user32" (ByVal dwFlags As Long, ByVal dx As Long, ByVal dy As Long, ByVal cButtons As Long, ByVal dwExtraInfo As Long)
Private Declare Function GetMessageExtraInfo Lib "user32" () As Long
Private Declare Function GetSystemMetrics Lib "user32" (ByVal nIndex As Long) As Long
Const SM_CXSCREEN = 0 'X Size of screen
Const SM_CYSCREEN = 1 'Y Size of Screen

Private Sub ScreenToAbsolute(lpPoint As POINTAPI)
lpPoint.x = lpPoint.x * (&HFFFF& / GetSystemMetrics(SM_CXSCREEN))
lpPoint.y = lpPoint.y * (&HFFFF& / GetSystemMetrics(SM_CYSCREEN))
End Sub

Private Sub Click(p As POINTAPI)
'p.X and p.Y in absolute coordinates
'Put the mouse on the point

mouse_event MOUSEEVENTF_ABSOLUTE Or MOUSEEVENTF_MOVE, p.x, p.y, 0, GetMessageExtraInfo()
'Mouse Down
mouse_event MOUSEEVENTF_LEFTDOWN, 0, 0, 0, GetMessageExtraInfo()
'Mouse Up
mouse_event MOUSEEVENTF_LEFTUP, 0, 0, 0, GetMessageExtraInfo()
End Sub
Per cliccare nel punto che vuoi tu usa
codice:
Dim p As POINTAPI 'struttura che contiene le coordinate da cliccare
p.x=100 'coordinata X del punto da cliccare
p.y=200 'coordinata Y del punto da cliccare
ScreenToAbsolute p 'converte il punto da coordinate dello schermo a coordinate "assolute" (espresse in 65536esimi di lunghezza/altezza dello schermo)
Click p 'clicca
.