I must confess to being a little confused, however. I just
pulled up an .xls I created that has some VBA code that I
wrote. I can view the code in the VBA editor. However,
it all seems to be part  of the same .xls.

In VB6, there is something called the "project" window. It
lists all of the .frm files and all of the .bas files. Further,
on the menu bar, there is a Project button  that facilitates
adding a form, module, etc. When I look in my directory tree,
I see all of the files associated with this project -- with
.frm and .bas extensions.

Where does any/all of this occur in Excel?