Reverse Compounding Mortgage Excel Interest Formula? Reverse Compound Interest?

Excel interest formula? reverse compound interest? - reverse compounding mortgage

I'm trying to compare my investment account compared to the S & P 500 in the last 5 years. I have a total of $ 15k (variable amount for the period of 5 years) and currently stands at $ 17.5K, which compound interest value can not win? IRR Calc is involved? What is the formula? I use the search solution, but I'm curious to attain a real formula. Thank you.