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 "Процесс № " & 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 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

Private Declare PtrSafe 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 PtrSafe Function IIDFromString Lib "ole32" _
        (ByVal lpsz As LongLong, ByRef lpiid As GUID) As LongLong
Private Declare PtrSafe Function AccessibleObjectFromWindow Lib "oleacc" _
        (ByVal hWnd As LongLong, ByVal dwId As Long, ByRef riid As GUID, _
        ByRef ppvObject As Object) As LongLong
        
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 "Процесс № " & 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 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