Formulas on a visible sheet cannot alter anything on another sheet or
anywhere for that matter.

Formulas return values to the cell in which they are written.

Back to first question...............

Yes, through VBA a user could alter values on a hidden sheet if they knew
the tab name or codename of that sheet.

Or they could run VBA to unhide the sheet and change everything on it.

Or even delete it.


Gord Dibben MS Excel MVP



On Fri, 12 Feb 2010 15:21:31 -0700, "Robert Crandal"
wrote:

Some of my sheets have been marked as "xlVeryHidden".
These sheets contain data that I do not want users to be
able to modify.

If a user knows the codename or tab name of any of
these hidden sheets, could they actually be able to
modify data on that sheet in any way?? Can they enter
a formula onto a visible sheet that references a hidden
sheet to change the data??

thank you!