CREATE TABLE #tblItems
        (
        ItemID int,
        ItemDescription varchar(50),
ItemDate smalldatetime
        );

 INSERT INTO #tblItems
        (ItemID, ItemDescription, ItemDate)
SELECT 1, 'Item 1', '01 Jan 2012' UNION ALL
SELECT 2, 'Item 2',  '03 Jan 2012' UNION ALL
SELECT 3, 'Item 10', '14 Jan 2012';

SELECT ItemID AS [Item ID] FROM #tblItems

DECLARE @SQLstring nvarchar(500)
DECLARE @ColName varchar(100)
SET @ColName = 'Order ID'
SET @SQLstring = 'SELECT ItemID AS [' + @ColName + ']  FROM #tblItems'
EXEC sp_executesql @SQLstring

DROP Table #tblItems

...
If @item = 'Job'
 then
    select 
       JobID = OrderID
      from #TblItems
 else if @item = 'Order'
    select OrderID = OrderID
      from #tblItems
...