(Seems like everything in OL is difficult)
Try this: Create a new e-mail message in OL and select your distribution
list from the Select Names window. Look at the distribution list name in
the "To" box and you should see a plus sign to the left of the list. Click
on the plus sign to open or expand the list. You will get a message warning
you that once you expand the list you cannot collapse it again. Click OK
(this has no effect on your list, just the current e-mail message). Now you
can delete anybody you want as an addressee of this e-mail without removing
them frokm your underlying list. You should also be able to add anybody you
want, too, also without necessarily adding them to your underlying list.