Problem with AecWall in AutoCAD VBA???

I am using AutoCAD Architectural Desktop 3.3, and I want to customize
it using VBA. When I try to run the example subroutine from the help
files, I encounter the following error:

Dim wall As AecWall
"Compile error: user-defined type not defined."

Do I need to take extra steps to include the AecWall type into the
autocad VBA environment?
How could I solve this problem?

Thanks!

Jim


Sub Example_EndPoint()

'This example displays the end point for the wall

Dim obj As Object
Dim pt As Variant
Dim wall As AecWall

ThisDrawing.Utility.GetEntity obj, pt, "Select a Wall"

If TypeOf obj Is AecWall Then
Set wall = obj
Dim pointStr As String
pointStr = Format(wall.EndPoint(0), "0.00") & ", " _
& Format(wall.EndPoint(1), "0.00") & ", " _
& Format(wall.EndPoint(2), "0.00")
MsgBox "Wall End Point: " & pointStr, vbInformation, "End
Point Example"
Else
MsgBox "Not a Wall", vbExclamation, "End Point Example"
End If

End Sub