Pivot - Dynamic Columns

Hello,

I am using MS SQL 2012.

I tried to get the output as shown in the image but how i can split the completed qty column also for each month. Tried few columns but no luck.

Expecting output as mentioned below.

StockItem <-> JobStage <-> OctAvg <-> OctQty <-> NovAvg <-> NovQty <-> DecAvg <-> DecQty

SELECT * FROM
(
SELECT  CONCAT(I.StockCode,'-', I.Description1) AS StockItem, J.JobStageId, Left(DateName( month , DateAdd( month , MONTH(STARTDATE) , -1 )),3) AS OnMonth
, CompletedQty
        , CASE WHEN DATEDIFF(MINUTE, CAST(StartDate AS datetime) + CAST(StartTime AS datetime),CAST(EndDate AS datetime) + CAST(EndTime AS datetime)) > 0 AND CompletedQty > 0 THEN
CAST(DATEDIFF(MINUTE, CAST(StartDate AS datetime) + CAST(StartTime AS datetime),CAST(EndDate AS datetime) + CAST(EndTime AS datetime)) AS numeric(18,4))/CompletedQty END AS ElapsedPcsTime
FROM JobStationFeat AS F
INNER JOIN StockItem AS I ON F.StockCode = I.Uniid 
INNER JOIN JobStage AS J ON F.JobStageId = J.Uniid 
WHERE StartDate >= '20151001' AND F.JobStageId NOT IN (11, 12)
) AS S
PIVOT
(
    AVG(ElapsedPcsTime)
    FOR OnMonth IN ([Oct], [Nov], [Dec])
)AS pvt1
ORDER BY StockItem, JobStageId

Thank you very much.