I have been working on a trading system using excel for a number of
years now. Recently I had a big break from a currency trader with a
large bank who wants to use the program and I want to privdee him with
a stand alone version that he can use to trade. The idea is to build a
track record with realmoney and then it could be sold potentially. The
problem I now have is to produce a program for him to use preferably
using excel but maybe in VB if better but it needs to be totally
secure in terms of the code as obviously I do not want to give years
of work away (if it is succesful then it could be worth a lot).

My question is fairly simple: is it possible for me to use some means
(i have heard blowfish encryption software could do it but it all
seems prohibitively complex to use) I can use to protect my code yet
make the program available to third parties (banks for example). I am
also interested in a means of having way of having the program
disable itself unless an email or web update unlocks it again.

Any pointers/advice would be much appreciated. Kind regards, Mark