i'm trying to build a model that's based on cumulative quarterly S&P 500
returns. however, rather than using the actual returns (that only come out at
each quarter's end), i want to create a quarterly return for each week based
on the weekly returns for the previous 13 weeks. i have yet to find a
function in excel that will take a set of interest rates over equal periods
and return the effective (cumulative) rate for that period. can anyone help?