Err.Raise only works in module, but not a sheet or workbook - excel

Question

I'm learning error handling and I think I'm getting the hang of it. But I've come across an interesting behavior. I'm handling my errors in my class modules, and I bubble the errors up the stack. I have traceability so when the error reaches the caller (or top of stack) an error is displayed telling me where it occurred at. It works just fine if the class is being called from a module. BUT if the class is being called from the sheet or workbook, then it generates an unhandled runtime error.
For example, take the following code:
sub testError
err.raise -1000,,"This is a custom error"
end sub
If I run this in a regular module I get the following:
But if I run that exact same code in a sheet or workbook, I get the following:
So some of my classes are being called from macros located on a sheet. Others are being called from workbook and/or sheet events. And if a handled error happens down the line, I get an unhandled runtime error without any useful information.
I can move my macros to a standard module. But I can't move my events (value changes, new caluclation, etc) to a standard module.
So I have two questions. Why can't I do err.raise in a sheet / workbook?
What should I do instead?
Thanks.

Answer 1

So digging into this further. There are two kinds of error popups VBA will give you:
One with a continue/end/debug/help button
One with an okay/help button.
It turns out you can only modify the description with the popup that has the end/debug button. (via the err.raise).
What determines which popup you see is where the top of your stack is. If its in a standard module, you'll get the "end/debug" popup. If its in a sheet/workbook object, then you'll get the "okay/help" popup.
Unhandled errors bubble up all the way to the top stack. If that stack is in a standard module, then you'll have the option of pressing the debug button, which will take you to the line that you're error occurred. If the top stack is in a sheet/workbook, you'll have no idea where it happened.
To illustrate my point, take the following code that will throw a standard runtime error:
sub testError
dim a as long
a = clng("X")
end sub
If this method is ran in a standard module you'll get this:
If you run this in a sheet / workbook you'll get this:
The later doesn't really work well with err.raise (you can't edit the description).
My problem is I have macros and events that are initiated in the sheets / workbooks. Those methods then call other methods in a module. But since the top stack is located in a sheet / workbook, the wheels come off of my error handling.
So my work around is to initiate my module level methods in a way that puts those methods at the top of the stack, and then it works:
'standard module
sub createClass
dim myObj as myClass
set myObj = new myClass
call myObj.raiseError
end sub
Instead of calling this method from the sheet / workbook as so:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
call createClass
End Sub
Do this:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
application.run "createClass"
End Sub
Doing it this way will place the createClass method at the top of the stack. and since this is in a standard module, the error handling will work as expected.