Hello Jorge,

I am attaching a sample illustrating how the sum of the selected row's values in a column can be obtained. Additionally, I've also added a function to allow summing of all row's values when the header checkbox is clicked for your reference. Note that the sample also illustrates how the datasource can be configured to display the sum of child rows in a parent row's field.

Hope this helps. Please feel free to contact me if you have any questions.