Best way to find 'new' transactions in closed period

Hi,

Is there a way to customize an account register report where you can tell what transactions are new, or have been updated recently (in particular, outside of the posting period)?

I can't find a transaction date modified field in the customize view, but we have found that the account in a closed period keeps moving (which we have found is due to FX credit note movements), but we also have some large transactions that seem to be appearing, and need to know an easy way to identify them so we can find out who is posting transactions to a closed period.