OK I understand I cannot make a wb entirely crack proof however I'm
trying to cover all bases to get it as close as possible. I'd
appreciate if anyone could spot any weakspots in the below process
i've written or suggest any other ways to make it more difficult for
the nasty people trying to get in!;

1. If wb opened with macro's disabled only a splash screen is visible,
all other sheets are very hidden (obviously wb and vb are protected
with very long alphanumeric passwords)

2. On first use wb creates a code (based on computer name and date)
and asks for an activation code (given to them by me). 3 attempts at
inputting the wb code and the wb deletes all sheets (no warning for
sheet deletion)

3. Once activated the wb is valid for 90 days or 30 uses, when it will
then ask for another code. 3 attempts and workbook deletes all sheets
(this won't be a problem as wb is not used to store data). No warning
for sheet deletion (to prevent users looking for the code)

4. If wb used on another computer it will recognise it is not the
computer activated on and ask for another activation code as per step
2.

5. wb code well hidden among rubbish and the sheet storing the data is
set to very hidden, plus the actual data on the sheet is hidden among
lots of ubbish! If this data deleted the main code modules will not
run as they check for this data being in place and if not there sheets
are deleted

This way basically wb cannot be distributed to other users, and
certain users could not use the wb after a certain length of time or
number of uses without an activation code. If a user discovered the
security code and deleted it the main code module would check for this
and delete all sheets.

How does that sound?!!