How to Use AccessibleObjectFromWindow API in VBA to Get Excel Application Object from Excel Instance Window Handle

Question

I need to get the Excel.application object from a window handle using AccessibleObjectFromWindow. I can't seem to make the code work. First, I successfully search for the XLMAIN windows. Then, when I get a handle, I execute the AccessibleObjectFromWindow
function. It seems to return a value of -2147467262 in all cases. Therefore, I believe that it is returning an error value. I can't figure out how to determine the meaning of this value.
If it is an error value, I believe that one or more arguments are in error. My best guess at present is that the GUID argument is incorrect. I have tried two GUID values: {00020400-0000-0000-C000-000000000046} and {90140000-0016-0409-0000-0000000FF1CE}.
I have seen both used in conjunction with OBJID_NATIVEOM. Neither one seems to work. I really would prefer not to use the second one as it has an Excel major and minor version number. I would hate to have to change this code, if a new minor version appeared.
The attached code has been commented to show which parts have been shown to work and which not. I'm at my wits end and really need help.
Thanks
'This module is located in Access 2010, but this is an Excel question.
Option Compare Database
Option Explicit
' Module-Level Declarations
'The GetDesktopWindow function and FindWindowEx function work just fine.
Public Declare Function GetDesktopWindow Lib "user32" () As Long
Public Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" _
(ByVal hWnd1 As Long, _
ByVal hWnd2 As Long, _
ByVal lpsz1 As String, _
ByVal lpsz2 As String) _
As Long
'I'm not getting the expected output from this function (see below)
Private Declare Function AccessibleObjectFromWindow& Lib "oleacc.dll" _
(ByVal hwnd&, _
ByVal dwId&, _
riid As GUID, _
xlwb As Object)
Type GUID
lData1 As Long
iData2 As Integer
iData3 As Integer
aBData4(0 To 7) As Byte
End Type
Function ExcelInstances() As Long
' Procedure-Level Declarations
' Value of OBJID_NATIVEOM verified by checking list of Windows API constants _
on this site: http://www.lw-tech.com/q1/base.htm
Const OBJID_NATIVEOM = &HFFFFFFF0
Dim hWndDesk As Long 'Desktop window
Dim hWndXL As Long 'Child window
Dim objExcelApp As Object 'Final result wanted: Excel application object
'Following variable (xlapp) to be set by AccessibleObjectFromWindow function
Dim xlapp As Object
Dim IDispatch As GUID 'GUID used in call to AccessibleObjectFrom Window function
'Set up GUID to be used for all instances of Excel that are found
Dim tmp1 As Variant 'Return value from AccessibleObjectFromWindow
' Executable Statements
SetIDispatch IDispatch
IDispatch = IDispatch
'Get a handle to the desktop
hWndDesk = GetDesktopWindow 'This seems to work
Do
'Get the next Excel window
'The following statement seems to work. We are finding and counting _
correctly all the instances of Excel. hWndXL is non-zero for each _
instance of Excel
hWndXL = FindWindowEx(GetDesktopWindow, hWndXL, "XLMAIN", vbNullString)
'If we got one, increment the count
If hWndXL > 0 Then
'This works. We correctly count all _
instances of Excel
ExcelInstances = ExcelInstances + 1
'Here is the problem. The following statement executes and returns a value of _
-2147467262. xlapp, which is passed by reference to AccessibleObjectFromWindow, _
is set to nothing. It should be set to the object for Excel.application. _
I believe that this value is not an object. I tried to reference tmp1. in the _
immediate window. There was no Intellisense.
'I think that the function in returning an error value, but I can't figure _
out what it is. I believe that AccessibleObjectFromWindow returns error _
values, but I don't know where to find their values so I can interpret the _
function's results.
'As best I can tell, the hWndXL parameter is correct. It is the handle for _
an instance of Excel. OBJID_NATIVEOM is set correctly (see constant declaration _
above). xlapp is passed by reference as a non-initialized object variable, which _
will be set by AccessiblObjectFromWindow. IDispatch may be the problem. It is set _
as shown below in the procedure SetIDispatch(ByRef ID As GUID). This procedure _
appears to work. I can see that IDispatch is set as I intended and correctly _
passed to AccessibleObjectFromWindow.
tmp1 = AccessibleObjectFromWindow(hWndXL, OBJID_NATIVEOM, IDispatch, xlapp)
'Need to write code to test tmp1 for error. If none, then set objExcelApp = _
object. Also, I exect xlapp to be set to Excel.application
End If
'Loop until we've found them all
Loop Until hWndXL = 0
End Function
Private Sub SetIDispatch(ByRef ID As GUID)
'Defines the IDispatch variable. The interface _
ID is {90140000-0016-0409-0000-0000000FF1CE}.
'NOT USING {00020400-0000-0000-C000-000000000046}, _
which could be the problem
'9 is release version - first version shipped (initial release)
'0 is release type - retail/oem
'14 is major version
'0000 is minor version
'0016 is product ID - MS Excel 2010
'0409 is language identifier - English
'0 is x86 or x64 - this is x86
'000 reserved
'0 is debug/ship
'000000FF1CE is office family ID
With ID
.lData1 = &H90140000
.iData2 = &H16
.iData3 = &H409
.aBData4(0) = &H0
.aBData4(1) = &H0
.aBData4(2) = &H0
.aBData4(3) = &H0
.aBData4(4) = &H0
.aBData4(5) = &HF
.aBData4(6) = &HF1
.aBData4(7) = &HCE
End With
End Sub
DaveInCalabasas

Answer 1

I don't think you can return a reference to Excel's main window like that as you are attempting to do.
Ref:
http://msdn.microsoft.com/en-us/library/windows/desktop/dd317978(v=vs.85).aspx 
It's relatively straightforward to return any workbook's window in any given instance, and in turn it's parent Excel app. Try the following and adapt as required (and include error handling) -
Option Explicit
Private Declare Function FindWindowEx Lib "User32" Alias "FindWindowExA" _
(ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, _
ByVal lpsz2 As String) As Long
Private Declare Function IIDFromString Lib "ole32" _
(ByVal lpsz As Long, ByRef lpiid As GUID) As Long
Private Declare Function AccessibleObjectFromWindow Lib "oleacc" _
(ByVal hWnd As Long, ByVal dwId As Long, ByRef riid As GUID, _
ByRef ppvObject As Object) As Long
Private Type GUID
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(7) As Byte
End Type
Private Const S_OK As Long = &H0
Private Const IID_IDispatch As String = "{00020400-0000-0000-C000-000000000046}"
Private Const OBJID_NATIVEOM As Long = &HFFFFFFF0
Sub test()
Dim i As Long
Dim hWinXL As Long
Dim xlApp As Object ' Excel.Application
Dim wb As Object ' Excel.Workbook
hWinXL = FindWindowEx(0&, 0&, "XLMAIN", vbNullString)
While hWinXL > 0
i = i + 1
Debug.Print "Instance_" & i; hWinXL
If GetXLapp(hWinXL, xlApp) Then
For Each wb In xlApp.Workbooks
Debug.Print , wb.Name
Next
End If
hWinXL = FindWindowEx(0, hWinXL, "XLMAIN", vbNullString)
Wend
End Sub
'Function GetXLapp(hWinXL As Long, xlApp As Excel.Application) As Boolean
Function GetXLapp(hWinXL As Long, xlApp As Object) As Boolean
Dim hWinDesk As Long, hWin7 As Long
Dim obj As Object
Dim iid As GUID
Call IIDFromString(StrPtr(IID_IDispatch), iid)
hWinDesk = FindWindowEx(hWinXL, 0&, "XLDESK", vbNullString)
hWin7 = FindWindowEx(hWinDesk, 0&, "EXCEL7", vbNullString)
If AccessibleObjectFromWindow(hWin7, OBJID_NATIVEOM, iid, obj) = S_OK Then
Set xlApp = obj.Application
GetXLapp = True
End If
End Function
Note as written if an instance does not have any loaded workbooks a reference will not be returned (though a workbook can be added using DDE, but convoluted!)
FWIW there are two other very different approaches to grab all running Excel instances though something along the lines of the above is simplest.
Peter Thornton