Add Check Box to Access database

Hi

I have a very basic access database which records some records that we hold in a file cabinet.  The database is about 2000 records and I need to add a check box field to it.  This I have done with no problems, however, when I check the box it checks it for all records instead of the current record only?  How can I configure the check box so that when it is selected it only affects the current record?

Thanks