Show cumulative totals
 

I am using a pivot table and have managed to get my pivot chart to show the
totals by month. My manager likes the ability to see the different impacts
of various cost types and budget fields by month, but he now wants is a
cumulative view for the entire 10 year period (i.e. have a running total cost
of the programme). I do not have this in my dataset and was wondering if
their was a chart type that showed this without rebuilding the entire dataset?