Hi Berlinda,
With a large number of cheque entries it's probably easier to delete the unposted bank rec., void the cheque(s), and the recreate the rec. This is one of the downsides with NAV's bank rec. process in that the cheque entries are essentially "locked" when they are brought into a bank rec. worksheet.
I guess Microsoft assumed most users would be completing and posting the reconciliation right away, but in practice I've seen a lot of clients who prefer to start the rec. at the beginning of the month and then continually work on it for a period of time. In fact, there is a suggestion submitted on Microsoft Connect from another user to change this behaviour so that cheques in unposted bank rec.'s may be voided without having to go through this workaround.
Regards,
Rob