ARS Provisioning policy for OCS - SIP = Email address

HelloWe have recently configured ARS in our environment. As part of our user provisioning policy we set up OCS and create the SIP to be the same as the email address. The problem is that when the SIP is created the email address for the new user hasn’t yet been created by Exchange. Due to this ARS defaults to the email alias@Windows Domain name which is wrong. I logged a call with Quest for this and they said there is no way around the issue without scripting some kind of SIP creation delay and suggested that I have a look on here. I would appreciate any help anyone could offer with this. I look forward to hearing your suggestions. Mark