demo version of my file

  • Thread starter Thread starter cw
  • Start date Start date
C

cw

Hi

I am looking to distribute an excel econometric model my colleague has
created and we would like to be able to offer a time limited demo on the
file. does any one know of anything that can do this.

i know i can create a macro that will check the date on startup of the file
and close if its past a certain date, but that is always easy to turn your
clock back to get round.

Thanks in advance
Craig
 
cw said:
i know i can create a macro that will check the date on startup of
the file and close if its past a certain date, but that is always
easy to turn your clock back to get round.
Click to expand...

If you suspect your potential customers would be dishonest, Excel is
absolutely the wrong platform to use for your product. Excel provides
only very weak IP security. It's simple to break worksheet and
workbook protection on your own, cheap to buy products to remove those
passwords and VBA Project passwords, and thereby eliminate the code
that could be used to implement an expiration date.

The only secure and robust security Excel provides is the file-open
password. You could use a compiled executable (.EXE file) to check the
expiration date (there should be code available somewhere on the web
for this that uses methods other than checking the system date), and
if not expired link to a running Excel instance or launch Excel if
it's not already running and open your workbook with its password.
It'd be simple to obscure the file-open password using a cypher, then
apply the inverse cypher just before using the password.
 
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