I tried braking it down
1. I started with the unmodified supervisor name - it worked
2. displayed original supervisor name fields and extracted LN with group by and it worked
3. added first name to the query (original sup name, last name extracted) and this is when I get the error. I tried just running the query with the first name extracted and I still get the error. here is the code if it helps any:
SELECT Left([SupervisorName],InStr([SupervisorName]," ")-1) AS FN
FROM tbl_EmployeeData_EODinfo
GROUP BY Left([SupervisorName],InStr([SupervisorName]," ")-1);