Implement SMALL function (https://support.office.com/en-us/article/SMALL-function-17da8222-7c82-42b2-961b-14c45384df07 ), which returns k-th smallest value from a range:

SMALL(array, k)

Workaround: This could be implemented as a custom function: http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/custom-functions.html