You can add VBA so that after a particular date all the sheets and
modules get removed.

You can also add VBA so that if an Excel document is opened somewhere
other than the corporate network posts an email message to a web
server that gets submitted transparently - as far as the user is
concerned.

You can add a blurb that warns the user that distribution of the sheet
may result in termination or legal action. Add a little checkbox in
there just for effect.

But it's VERY easy for a non-technical person-Excel-user to work
around ALL that.

What you want to do can't be done.

The CLOSEST you can get is to store the data in a pdf or flash file
and make it so the document can't be saved locally. You can make the
report 1600 pixels so it can't be easily screen captured.

For starters it might also set the file up in a web site or Sharepoint
server that requires NT authentication. Then tell users always to
access the file through a particular link.

But no matter what, users can screen capture the data and save it.

According to the Wall Street Journal, Microsoft, In its European Anti-
Trust law suit, didn't submit it's techincal documents to regulators.
Instead the regulators had to fly out to Redmond and read documents in
a small room where a security guard watched their every move. No
cameras. The regulators had to come at their own expense which annoyed
them like crazy.