Change a filetype's "edit with" independent of "open with"?

Under Windows XP, I could go into Folder Options, select File Types, and use
the "Advanced" option to select not only which program opens a file, but
which (potentially different) program "edits" that file (when "edit" is
selected using the right-click menu). So, for example, .htm could be set to
open by default with Firefox but edit by default with Notepad.

I cannot find any way to achieve a similar result using Vista Beta 2. I can
use the Default Programs control panel to associate files with ONE program,
but only one program. Under the above example, I can theoretically use
Internet Options to set Notepad as the default editor, but Vista apparently
doesn't care and insists on "editing" with Word. But I would like to regain
the kind of control I had generally (so, for example, I could "open" jpeg
files with one program but "edit" them with another, etc.).

For what it's worth, I poked about in the Registry for a bit
(HKEY_LOCAL_MACHINE\SOFTWARE\Classes), but Vista didn't seem to care very
much. If there exist any other tricks, they lie beyond my Googling skills.

Am I missing something obvious (or, if I'm missing it, my ego hopes it's at
least subtle), or is this functionality just plain missing? If so, I
sincerely hope it's merely an artifact of this being a beta version of the OS.

If anyone can help, I'd really appreciate it.