select JobNum, RefreshDate, RecID from ClosedJobsSumms

UPDATE cjs
SET RefreshDate = '20120822 08:00'
FROM ClosedJobsSumms cjs

UPDATE cjs 
SET    QtyOrdered = QtyOrds.qtyord 
FROM   ClosedJobsSumms cjs 
       INNER JOIN (SELECT o.job_number, 
                          Sum(o.qty_ordered) AS QtyOrd
                   FROM   ERPDB.dbo.orders o 
                   LEFT JOIN ClosedJobsSumms cjs1 
                          ON cjs1.jobnum = o.job_number 
                   WHERE  cjs1.jobnum IS NOT NULL 
                          AND cjs1.custid IS NULL 
                   GROUP  BY o.job_number) QtyOrds 
               ON QtyOrds.job_number = cjs.jobnum

CREATE TABLE #T (
JobNum INT,
RefreshDate DATETIME,
RecID INT);

INSERT INTO #T (JobNum, RefreshDate, RecID)
VALUES (1,GETDATE(), 1),(2,GETDATE(),2);

UPDATE T
SET RefreshDate = '20120822 08:00'
FROM #T T;

SELECT *
FROM #T;

exec sp_who2;

UPDATE cjs
SET RefreshDate = '20120822 08:00';

UPDATE cjs
SET RefreshDate = '20120822 08:00'
FROM ClosedJobsSumms cjs

--SELECT
--    {column-names...}
UPDATE {table-name-alias}
SET ...
FROM {table-name}
...

SELECT
    {column-names...}
--UPDATE {table-name-alias}
--SET ...
FROM {table-name}
...