========= MS Access 2003 Help ==============
When can I update data from a query? (MDB)
Data can't be updated
...
Query or query field
Query that calculates a sum, average, count or other type of total on the
values in a field, or an update query that references a field in the Update
To row from either a crosstab query, select query, or subquery that contains
totals or aggregate functions

Solution
By using a domain aggregate function in the Update To row of an update
query, you can reference fields from either a crosstab query, select query,
or subquery that contains totals or aggregate functions.
========= MS Access 2003 Help ==============