After setting a db to offline it wont be available for a restore, however, you put all statements in a single transaction

--Step1

alter database <dbname>

set offline

with rollback immediate -- this is the part that kills the connections

--Step2

alter database <dbname> set online

restore database <dbname> <restore parameters>

Credit: This was actually given to me by an on call DBA. Nice alternative instead of having to shutdown IIS on all my web servers to do a db restore./b]