I am trying to total 3 different Running totals. Is this possible?

Here is an example of what I am trying to do. Let's say that there is a grouping on a job no 100 where I am totaling parts for that job. I have a running total on Part X, Part Y, Part Z. Is there a way to add up all of these parts? My problem is when one part isn't used for that job. It doesn't give me a total then.

Please always say what version you are using. In 2005 use CUBE/ROLLUP. In 2008 use GROUPING SETS.

SELECT JobNo, PartNo, SUM(Quantity) Quantity
FROM Stock
GROUP BY PartNo,JobNo WITH ROLLUP;

SELECT JobNo, PartNo, SUM(Quantity) Quantity
FROM Stock
GROUP BY GROUPING SETS ((JobNo,PartNo),(PartNo),());