You could add a UDF to AR_Salesperson that could be used to identify the old records.  The lookups could then be setup to filter out those records.

You could add a UDF to AR_Salesperson that could be used to identify the old records.  The lookups could then be setup to filter out those records.

I've used this approach before and it worked great.  A simple checkbox UDF will suffice.

You can create a system default view for the salesperson lookup where you filter on the UDF.

If you delete the record in AR_Salesperson, you could end up causing some # 11 errors to occur in any task that attempts to read the AR_Salesperson table for the key that is in another table.  The various inquiry tasks may not produce the error but they will only hold the salesperson record's key (in the SalespersonDivisionNo and SalespersonNo) in them and not other fields like their name.  So even if an error is not produced in the inquiry tasks, you will only see the salesperson number and not any other details.  You may also want to make sure there aren't any records in AR_OpenInvoice with the salesperson numbers that are no longer valid.  If you have any custom reports or modified reports/forms that link add the AR_Salesperson table, you will no longer have a valid link between the tables if using an INNER JOIN which will cause records in the other table to be omitted.