This example shows how to implement custom group intervals in Pivot Grid to group axis values.
The Product Groups calculated field is bound to the following expression:
Iif(Substring([Product Name], 0, 1) < 'F', 'A-E', Substring([Product Name], 0, 1) < 'T', 'F-S', 'T-Z')
The expression groups the Product Name field's values into three large ranges: A-E, F-S, and T-Z according to product's start characters.