By default RadPivotGrid sorts the data ascending or descending. If you want to control the sorting, you can modify the type of items which you want to sort in order to include an additional property which will be the sorting key afterwards. You will need to implement CompareTo and Equals methods so you can compare the sort keys as required. I have prepared and attached a sample project which demonstrates the exact approach (the class MyProduct has SortKey property which defines the order).
Hope this helps.
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