Help With Pivot for getting cumulative data!

[Karthik-Excelsior]

I've a small but an urgent question re. Pivot tables. How to pivot a table with cumulative values? I've to look at the week over week performance stats, and I'm using Pivots to see what has been the performance in Wk1 (10 units), Wk2 (15 units), Wk3 (8 units), etc. However, what I would like to see is the cumulative number for each of the weeks Wk1 (10 units), Wk2 (25 Units), Wk3 (33 units), etc. Is that poss? If so, how? Thx a bunch in advance!