I posted this the last time there was a discussion about CSV and excel:

If you are generating the CSV yourself, save yourself some agony and just wrap the text in =""

    $ cat test.csv
    ="12.34567890124312341234123412341234",="1-5"
    $ open -a Microsoft\ Excel test.csv

https://news.ycombinator.com/item?id=5514587

Explanation:

It uses another auto trick: if the leading character is '=', the result is treated as a formula.

Thus, you can actually write formulas in your CSV and excel will interpret appropriately:

    $ cat test.csv
    =1+1,="1-5"
    $ open -a Microsoft\ Excel test.csv

You should see the value '2' (with content `=1+1`)

https://news.ycombinator.com/item?id=5514704