Problems simulating mouse clicks using SendMessage

[Tazo]

I have been trying this for around 2 and a half hours now, to no avail. For whatever reason, the program I am sending the click to ( Firefox ) isn't reacting. It is supposed to click one of those option box things. I am totally clueless as to why it won't work..

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
 
Private Const WM_LBUTTONDOWN = &H201
Private Const WM_LBUTTONUP = &H202
Private Const GW_CHILD = 5

Private hWndParent As Long
Private hWndChild As Long
'-----------------------------------------------------------------------------'

Public Sub SendClick(lnghWND As Long, x As Long, y As Long)

    Dim iResult As Long
    Dim lParam As Long
   
    lParam = (y * &H10000) + x
    Debug.Print "lParam is: " & lParam & " || lnghWND is: " & lnghWND & " || x is: " & x & " || y is: " & y

    iResult = SendMessage(lnghWND, WM_LBUTTONDOWN, 0&, ByVal lParam)
    iResult = SendMessage(lnghWND, WM_LBUTTONUP, 0&, ByVal lParam)
   
End Sub
Private Sub Command2_Click()

    Debug.Print hWndChild
    Call SendClick(hWndChild, 296, 701)

End Sub

Private Sub Form_Load()

    hWndParent = FindWindow(vbNullString, "Index - Mozilla Firefox")
    hWndChild = GetWindow(hWndParent, GW_CHILD)
    Debug.Print "parent: " & hWndParent
    Debug.Print "child: " & hWndChild

End Sub

I am always getting a correct parent/child value, so that isn't the problem. I am also positive that my X,Y coords are correct.

Any help is appreciated.