Difficult Select Statement for a Newbie

as soon as I add the "Avg" function I get the error message below. If I remove the AVG I get just the first value from the first row. I'm trying
to retrieve the Top 3 records then average col1. Any help please?


SELECT DISTINCT TOP 3 Avg(col1) AS some_name, col2 FROM some_table WHERE col2 = '" & some_var & "' ORDER BY col2"


Microsoft JET Database Engine error '80040e21'

You tried to execute a query that does not include the specified expression 'userid' as part of an aggregate function.

You can must group the non aggregrate column if you are attempting to retrieve more than on row.
SELECT avg(col1), col2 from some_table
where col2 = something
GROUP BY col2