Fail to Loop Through Items in a SelectionSet

I am trying to use VBA to loop through all the items in a selection-set
to find their patterns. Unfortunately, I keep getting the following
error message when I use Item() method of the selection-set to try to
get acess to an item in the selection-set:
Error Number: -2147418113
Error Description: Automation error Catastrophic failure

The following is a sample program that shows the error:

Private Sub SavePcInfoToArray()
'Save the info of all the pieces into an array.

Dim objSelectSet As AcadSelectionSet
Dim anFilterTypes(0) As Integer
Dim avFilterValues(0) As Variant
Dim nCur As Integer
Dim objItem As AcadEntity

On Error GoTo Err_SavePcInfoToArray

Set objSelectSet = ThisDrawing.SelectionSets.Add("AllPcs")

anFilterTypes(0) = 8
avFilterValues(0) = "My_Rect"
objSelectSet.Select acSelectionSetAll, , , _
anFilterTypes, avFilterValues

'Here, the program shows the correct number of
'items selected. So far so good.
ThisDrawing.Utility.Prompt vbCrLf & _
"Total Pieces Selected: " & objSelectSet.Count

'Trying to get access to the three items in the
'selection set. But failed at Item() method.
If (objSelectSet.Count = 3) Then
Set objItem = objSelectSet.Item(0) <-- Fail right here
Set objItem = objSelectSet.Item(1)
Set objItem = objSelectSet.Item(2)
End If

objSelectSet.Delete
Exit Sub

Err_SavePcInfoToArray:
If (Not objSelectSet Is Nothing) Then
objSelectSet.Delete
End If
MsgBox "Error # " & Err.Number & ": " & Err.Description
Exit Sub
End Sub

I am wondering whether this may have something to do with the fact that
I use a third party software called CAD-Duct to add those three items
onto the drawing. The reason why I have this suspicion is that the
same program can get access to a generic rectangle that I use plain
AutoCAD graphic to draw it instead of using CAD-Duct -- meaning that
the generic rectangle becomes the Item(0) of the selection-set. The
result is like this:

If (objSelectSet.Count = 4) Then
Set objItem = objSelectSet.Item(0) <-- It is OK
Set objItem = objSelectSet.Item(1) <-- Fail right here
Set objItem = objSelectSet.Item(2)
Set objItem = objSelectSet.Item(4)
End If

Seem like somehow the three items that I draw using CAD-Duct becomes
hidden when I use Item() method to try to get access to it. How can I
get around with this problem?

Thanks in advance for any help.

Jay Chan

 

Turns out the properties of the items that are drawn using CAD-Duct is
in a different format than regular generic items that are drawn using
pure AutoCAD. That explains the reason why I cannot use Item() method
to get access to the properties of the items drawn using CAD-Duct.

Based on some past posts in a different forum, I am supposed to be able
to get around with this problem by installing something called Object
Enabler that I can download from CAD-Duct web site. Unfortunately,
that Object Enabler trick doesn't work in AutoCAD 2007 that I am
currently using. In other words, this is yet another deadend.

The bottom line is that I cannot use VBA to get access to properties of
items drawn by CAD-Duct as long as I am using AutoCAD 2007.

Hope this info helps something to avoid the pitfall.

Jay Chan