SQL update query syntax with inner join

The SET needs to come before the FROM\JOIN\WHERE portion of the query.

UPDATE CE
SET sJobNumber = AD.JobNumber
FROM CostEntry CE 
    INNER JOIN ActiveCostDetails As AD 
        ON CE.lUniqueID = AD.UniqueID
WHERE CE.SEmployeeCode="002"
    AND SubString(CostCentre, 1, 1) = sDepartmentCode
    AND substring(CostCentre, 3, 1) = sCategoryCode
    AND substring(CostCentre, 5, 2) = sOperationCode