Question on CIW

Hello All,
In our organization majority of the users are on Office XP and now we are
starting the upgradation to 2003.
I have created the MST file and found that it is geeting applied correctly.
But now I got stuck up here,In outloolk I want to edit the existing profile,
because by default we want cached mode to be enabled for all of the users.
After mentionining the user name as %username%, I don't know how to specify
the exchange server name. Because the mailboxes are distributed among two
exchange servers. I know this value corresponds to HOMESERVER, but how will
specify the exchange server, because I want to depploy it without much manual
intervension. Is there any general expression for exchange server like we
represent the currently logged in user as %UserName%?
Any pointers and Help is highly appreciated.