I need to create a grid that will use the grouping feature.
For each group I need to have 2 totals rows (summaries) which are calculated this way: the first total is the sum of the first 3 rows before it, and the second the sum of the previous total and some other row.
You will have to create this, as we do not support this by default. I believe there are some 3rd party options availble. You may have to search around and find one close to fit your needs. I will look around.