Multiple changes in Exchange on AD

I need to make a change to many individual mail boxes on an Exchange 2000 server running AD in native mode.(e.g. remove an email address from 250 mailboxes)
In Exchange 5.5 we could export the list into Excel, make changes and import them back.
It appears that this task is much more difficult in a 2000 environment.
Exporting the list is easy enough but it is the importing after changes have been made in Excel that seems to be the problem.
Does anyone know of a utility that will allow me to do the import.
Many thanks