Great, glad it helped.
Btw, note that you must ALWAYS use the alias in the UPDATE statement when using a join in an UPDATE.
UPDATE Brs --<<--WRONG!! MUST be (alias) B
SET HrsHKB = M.HRSWERK
FROM dbo.Brs B --<<-- alias assigned to table, as it should be
INNER JOIN MYCTE M
ON M.IDHuis = B.IDHuis AND
M.zzpclient_id = B.zzpclient_id
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial: "If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them."