Post only in primary ledger

1.-A Primary book and a secondary book have been configured.

2.-The currency of the primary book is MXN and the currency of the secondary book is USD.

3.- Each book has an independent exchange rate from one another.

Facts:

Exchange rate for secondary book is not loaded.

When I try to send to posting, the system sends me an error because the exchange rate for the secondary book is not loaded.

Is it possible to post to the primary ledger only and then post to the secondary ledger once the exchange rate for the secondary ledger is entered?

Thanks

Manuel