Provide function to allow users to get n-th event before/after a certain time

Provide the functionality in AF analytics to get the nth event of an attribute before/after a certain point in time where n is a variable. In cases where n is small or fixed we can use the PrevEvent() or NextEvent() functions n times to do this, perhaps with some IF statements to handle small variations in n. This is not practical for cases where n is large or varies over a large range of values,