Adding Exchange rights to AD 2008 users without mailboxes

After posting in an older question I gave up temporarily. On a side search I found an answer to my problem and it works. However it is time consuming and where several accounts exist I'd like a quicker way to modify the advanced attributes of an account rather than via the Attribute Editor in AD Users & Computers MMC.

See: http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_26262511.html for more info.

Basically what has been happening is at the start of the year 100+ accounts were bulk created using csvde and for some reason in the creation process the default Exchange attributes were not passed onto a multitude of these accounts.

To allow the users to link into Exchange there are 2 ways of doing it, delete & recreate each account and then get phone calls when users passwords are reset, etc, reset user share attributes (SID's) or edit each account & copy & paste several long account settings into their AD account.

What I want to know is if there is some way using CSVDE for example to MODIFY an account rather than export/import..

I had a look at dsmod but it looks like the extended attribute set isn't available.

Extended attribute set needing modified (defaults):
homeMDB
homeMTA
msExchHomeServerName
msExchRecipientDisplayType
msExchRecipientTypeDetails
msExchVersion
showInAddressBook

Per-user attributes:
legacyExchangeDN
proxyAddress
textEncodedORAddress

Any help would be appreciated