Making an Excel spreadsheet harddrive copy inoperable from a macro
 

Hi
I made a game on an Excel spreadsheet that will automatically play one hand
after the other continuously.
I plan to offer a free demo that will automatically stop after playing a
certain number of hands and then you are unable to play any more.
This is all working fine.
The problem is, you are able to reload the original file from the
harddrive and play the same certain number of hands again and again.

How do I stop this (being able to reload the origanal file from the
harddrive and playing addional hands on the new copy)?

Or would it be easier to have the limiting factor be a certain number of
days (say after 5 days the game ceases to work, even when loaded into Excel
from the harddrive?).
The problem is getting the "no more playing" information to the copy on the
harddrive from the macro.
Either way, how is it done?

Thankyou
Ed