SQL 7 missing records issue

I have 3 tables that have an ID field in common. Twice a year records are imported in from a file we receive from a governing board. If new records are found in the file, records are added to one of the tables, but the process leaves out the othertwo tables. (the process was developed before the other tables existed) I need to know how to insert records into the other two tables, duplicating the id and adding other info only for these new records. I’ve tried inderts and updates to no avail. Not sure what I’m missing. Any help would be greatly appreciated.