I created a spreadsheet for a friend and I want to protect it so that he
cannot mess up the formula's unless he saves it as a new file (save as).
That way he always will have the original to go back to.

Instead of file / save, use file / save as, when creating the file for your
friend. In the dialog that pops up, select Tools / General Options at the
top right, and select read-only. You could even choose to require a password
to open with write permissions.
(You may also want to use Windows Explorer to make the file read-only.
Otherwise, Excel will prevent saving over the file, but your friend could
still delete the entire thing).

"Chrisrmx" wrote:

I created a spreadsheet for a friend and I want to protect it so that he
cannot mess up the formula's unless he saves it as a new file (save as).
That way he always will have the original to go back to.