Adding files to an Excel menu

I've recently added a couple of frequently used files to the Work menu in Word (using Customize/Commands/Categories/Built-In Menus/Commands and then dragging the Work menu item to the main menu bar.)

This is a useful means of quick access to often used files without having to clutter up my auto-hide folders on the desktop with shortcuts. It works like the recently used files on the File Menu, except the files stay there until I decide to trash them. It works well for me.

I'm wondering if it's possible to do something similar in Excel? I know Excel has the Built-In Menus option but I can't work out how to add my frequently used files to it. None of the Commands seems to allow me to do it. I'm sure it must be possible, but I can't work it out.

Can anyone enlighten me? Thanks.