Excel switches back to fisrt sheet in a file

[Jethro[AGHL]]

I have run into a confusing issue. We have a dedicated NT4 PC that is
used to log data. Our production personnel use it to enter data into
Excel spreadsheets.
Now the file has quite a few macros in it but for working with the data.
All of a sudden what's happening is that if the spreadsheet is left open
for any length of time, it will automatically always switch to the first
sheet within the file.
Say they normally enter data on Sheet3, if left alone Excel with switch
to Sheet1.

We aren't sure if someone has tampered with the file but all the macros
are normally beyond their comprehension. Is there a setting someone to
cause this?

Thanks,
Jeff

 

[J.E. McGimpsey]

There are no settings that would do this. I'd suspect a timed macro
that selects sheet 1.