Andrew/Florina:

If I understand Florina’s question, you want to restrict the Bank Rec to allow posting only to current fiscal periods.
If you use set Ledger Fiscal Calendar each month/period and mark the periods you want as Open and Closed, then you can tell Bank Rec to obey these rules as well.

In Bank Rec, go to the Company Profile and on the Interfaces tab, there is an option: "Validate closed periods". This can be set to "Allow", "Warn Only" or "Disallow". Select "Disallow" and users should only be able to post to open periods.