Update/Delete on Table Join

Hi,
    I use a query below & it works fine. How would I change the query for updating the 'Norm' value from the 'Norms' table?

Any help appreciated.
Thanks
Paul.

SELECT
Materials.Category,
Norms.Material,
Norms.Task,
Norms.Norm,
Norms.IncPrice
FROM
Materials
LEFT JOIN
Norms
ON Norms.Material = Materials.Material
GROUP BY
Materials.Category,
Norms.Material,
Norms.Task,
Norms.Norm,
Norms.IncPrice