Life would be so much harder without excel, but it is doable and takes a lot more time. You are able to solve this mystery without having any knowledge about excel, but it will take a lot more time. But as in most cases, if you are persistent you’ll reach your goal or geocache. And besides, I’m a nice guy so you won’t have to try 15^10 different coordinates. If you’re not familiar with excel you will get clues along to the way to narrow your search and finally, like magic, end up with digits in green.