I have a pivot table in excel that I am using to find two values, one on each side of a maximum value (gaussian in shape). One pivot table is unsorted and the LOOKUP function finds the value I expect. To find the other value, I have a second pivot table sorted "Z to A" and then perform the same LOOKUP function. When sorted, it will not find the correct value even though I can see it in the list of values. If I unsort the pivot table, it works fine. Why would the function only work on unsorted data and not sorted? Is there a function I can use in its place? I've tried VLOOKUP and INDEX/MATCH and they fail the same way.