secondary ledger starting in a future period

We need a number of secondary ledgers that are subledger level to start in October. We want October to be the first period. However, when testing with a receivable in September the create accounting is erroring for the secondary ledger because its not in an open or future enterable period. We don't want any September activity to come over. October transactions will begin before the accounting team is done closing September. How do we get it to not try to send the September entries?