I'm trying to create a report based on the following information:

1. Points achieved for each period

2. Cumulative points achieved as at the end of each period

A period contains several tasks, each with a number of points attributed to it. Item 1 above, 'points achieved per period', is a summary total for all the tasks included in the period.

A sample data set (at summary level) is:

1. Points achieved each period:

   Period 1 - 0 points

   Period 2 - 10 points

   Period 3 - 8 points

   Period 4 - 4 points

2. Cumulative points achieved as at the end of each period:

   End of Period 1 - 0 points

   End of Period 2 - 10 points

   End of Period 3 - 18 points

   End of Period 4 - 22 points

Is there a summary formula I can use to achieve the cumulative values in item 2 above?

I've tried PREVGROUPVAL but it gives the following results:

   End of Period 1 - blank (presumably because there is no PREVGROUPVAL summary value before period 1)

   End of Period 2 - 10 points (period 1 + period 2)

   End of Period 3 - 18 points (period 2 + period 3)

   End of Period 4 - 12 points (period 3 + period 4)

I think the formula is working as expected - i.e. it takes the value for the previous summary period and adds it to the value for the current summary period.

What I need is a cumulative value as at each summary level. Any ideas please?