Problem enter calculus

I had downloaded a spreadsheet from yahoo finance.
Now i want to do some calculus with these data.
But when i do, for example,
" =(B3-B2)/B2 "
the result don’t appear and i have " #VALUE! ".
How can i use these datas downloaded from the internet?

“The most common reason for the #VALUE! error is that a formula is expecting numbers in a cell, but instead it finds spaces, text, or other characters.”

You might find a solution here already:

Also a screenshot might help.

okay, i have found after reading your link.
The datas i have copyed from yahoo finance was in english, so for example, 52.34 instead of 52,34 in France.
The ‘.’ was considered as a bit of text.

Now… how do i convert all these hundreds of datas, from 35.55 to 35,55?

Make sure the cells are not formatted to Text but Number, select the cells with wrong data and invoke the Find&Replace dialog, Search \. Replace , and under Options activate Regular expression, hit ReplaceAll.

Or install and use the CT2N Convert Text to Numbers extension.

Thanks, i have done exactly what you said