Create a copy in the same folder when a file is modified and saved

I have a excel file shared with multiusers with the write permission. In case
they save the file unintentionally, I want to create a back-up file of the
original one whenever the file is opened and resaved (The back-up file should
be the old one for recovery purpose!).

Is there a function in Excel to do this or need I create a Macro?

I just got the answer by looking at posts before. My next question is can I
back up the file into another different folder from the original one?

"Turboj" wrote:

> I have a excel file shared with multiusers with the write permission. In case
> they save the file unintentionally, I want to create a back-up file of the
> original one whenever the file is opened and resaved (The back-up file should
> be the old one for recovery purpose!).
>
> Is there a function in Excel to do this or need I create a Macro?