RBAC Quota

I would like to allow our helpdesk staff to change the quote size on users mailboxes using RBAC, and I have followed this guide to create a new management group;

http://blogs.technet.com/b/matabra/archive/2011/09/16/how-to-create-a-custom-recipient-management-group-using-exchange-2010-rbac.aspx

Also following this post it seems possible to do this on Exchange 2010 (SP1)

http://social.technet.microsoft.com/Forums/en-AU/exchange2010/thread/a2c7eb3f-9b07-4a9d-abba-afbed9fd75e0

looking at the above post on the 'set-mailbox' cmdlet I cannot see the parameters to set the settings below? (or in any other cmdlet under 'mail recipent' for that matter)

3,remove other parameters other than -Identity -IssueWarningQuota -ProhibitSendQuota -ProhibitSendReceiveQuota-UseDatabaseQuotaDefaults

I have the list below (and anyway how do you edit this list to remove parameters?)

{AcceptMessagesOnlyFrom, AcceptMessagesOnlyFromDLMembers, AcceptMessagesOnlyFromSendersOrMembers, Alias, AntispamBypassEnabled, ApplyMandatoryProperties, Arbitration, ArbitrationMailbox, ArchiveDomain, ArchiveName, ArchiveQuota, ArchiveStatus, ArchiveWarningQuota, BypassModerationFromSendersOrMembers, CalendarRepairDisabled, CalendarVersionStoreDisabled...}

Can anyone help please.

Thanks- John