You've probably solved this but this is how I do it. (I think the doc needs to be more specific about this.)
When you do the following:
handleError:
Call AddToStackTrace()<br/>
End Function
the AddToStackTrace function is adding the name of current function to the info but is handling the error. You need to throw the error yourself. Like this:
handleError:
Call AddToStackTrace()<br/>
Error Err, Error$ ' throw the error <br/>
End Function
This works for me and gives me the results I expect.