Dont use spreadsheets for any numbers that are important.
Just keep excel for displaying data.
Do not start puting code into spreadsheets - its never tested, always has bugs in.
There are a surprising number of large companys who base their decisions on storing and manipulating numbers. Its fuking nuts. No transation, no seperation of data and code. Limited testing - one had test and real data in the same file which, inevitably, got mixed up at some point.