Is it possible to create ones own property to an Excel object?

Example:

The workbook has some builtin properties, like...

ThisWorkbook.Path
ThisWorkbook.Name

etc...


I would like to create a...

ThisWorkbook.URL

....which, obvious, would return the URL from where on the Intranet (or
Internet :-) the user can always find the newest version of the workbook,
and also use this new property, in my own macros, for further programming,
like data links in the workbooks URL path.


I'm aware that it would probably require some sort of programming in the
Workbook_Open event, but that doesn't matter - just as long as I have the
property for the rest of the time that the workbook is open.


Possible?


TIA,