I have some data in an excel workbook and I wish to write some code to
extract one line (not so hard!). Where the problem arrives is I don't want
the user to see any of the other data in the worksheet (ever) - just that one
line that is extracted.

The macro (which would be converted to an add-in) would look like:
Load workbook
get one line of data
close workbook

But the user can hit <ctrl-break once the workbook is loaded and
see/examine the worksheet. What is the most secure method to use so that the
user cannot see the workbook? Would hiding the worksheets and protecting the
book work and macros work?

or alternatively would it be better to put the data into a database or csv
file?

Security is the paramount concern

Any Help Appreciated

Regards,