Anyone know how to do this on 4.1.2

Is there anyway of automatically forwarding a call to an external number when an IP phone de-registers.

I have been told that Unity 3.1 does not support Multi-Tenant, if so:What does the CCM service parameter "MultiTenantMWIMode" do ?, by reading the definition it states if you set this to true that you can use translation patterns to activate the MWI....