Basically, there are two options to handle this, when databinding the grid to this dataset, and/or performing calculations on this data.
The first is to merge the data, for example by using a join statement. This would allow you to pass the data and directly allow the control to make calculations with it.
The other would be to make custom queries to the related data, when binding the grid, or when supplying cumulative data - such as footer totals.
I hope one of these options is suitable for you.
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