Thank you for writing back.
Аdding the new column to the data source and passing this data source to the PivotGrid DataProvider must update the PivotGrid because the grid will pivotize a new column for the calculations.
I am not sure that I fully understand your intention. You can set the size to the particular column using the following code:
sender, EventArgs e)
"Sum of Freight"
node.PreferredSize = 300;
Please, bear in mind that this code should be performed when the UI is already built.
I hope this helps.
the Telerik team