Move mailboxes 2003 to 2010 but stop at 6am daily

I have the script to move a group of users from Exchange 2003 to Exchange 2010 and it works using Task Scheduler.  I want to kick off the script at 7pm but stop any mailbox moves after 6am.  Is there a way to do this in EMS?  In 2003 you could schedule a move and not process additional moves after a scheduled time.

I'm trying to avoid a mailbox being moved in the morning while the users arrives at his/her desk.