Changing working Directory useing abbrev ??

[William Case]

Hi;

I have the following path abbrevs in my ~/.emacs:
 '(directory-abbrev-alist (quote (("ppprac" .
"/home/bill/Docs/Stuff/PHPprac/") ("ocrepo" . "/home/bill/OclugRepo")
("workem" . "/home/bill/Docs/Work/emacs/"))))

These abbrevs work with my find-file command.  i.e C-x C-f RET workem
RET opens a new dired buffer "/home/bill/Docs/Work/emacs/" -- which is
what I want.

On the other hand, when I try 'M-x cd RET workem RET ' ( and various
imaginative variations) I get '[no match]'.

How can I use my path abbrevs to change to a new pwd??

Oh, by the way, I have googled and info-ed indeed.  I am still not used
to using all the correct search criteria, so the explanation is there
somewhere I am sure, but I can't find it. 

-- 
Regards Bill