Your real problem is insufficient error handling code. For a program to be
reliable, it must check the result of every SET statement. That may sound
extreme, but it is true. Any attempt to set an object variable can fail at
runtime, due to circumstances you cannot anticipate as you write the code. This
is especially true when using automation to operate another program like
AutoCAD.
Some functions raise an error when they fail, while others just return Nothing.
You are getting Nothing, and using the variable anyway, very likely in code
that's far removed from where you supposedly set it. That's why it is essential
to check the result of every SET statement immediately, so the problem is
identified at its source, not somewhere down the road.
To solve your immediate problem, you can start adding these checks in the module
that's calling the Lisp routine, and keep adding them to every module that is in
the code stream for this operation. Just stick a call like this after each SET
statement:
On Error GoTo Failed
Set XXX = blah blah blah
AlertNothing XXX, "XXX", FuncName, Where
...
Failed:
' Whatever
In a code module:
Public Sub AlertNothing(ByVal SomeThing as Object, ByVal What as String, ByVal
Who as String, ByVal Where As String)
If SomeThing Is Nothing Then
MsgBox "Variable " & What & " in module " & Who & " at " & Where,
flags>,"Set Statement Failed:"
' You might even raise an error here, in addition to or instead of the
message box
Err.Raise ...
EndIf
End Sub
Good Luck,
Mark Holder
