Hmmm...Here's a few suggestions, though I'm not a VB programmer:
1) Encrypt it using a password that you can setup on both ends.
2) If VB doesn't have an easy-to-use encryption function and it does have a hashing function, hash the password against a secret seed and use that with the
One-time pad - Wikipedia, the free encyclopedia method. This assumes that your hashed code will be used only once, of course.
3) Failing the above 2 methods then ... Not totally sure as encryption is not available then. I can think about it more if you don't have the above 2 options and other suggestions are encouraged!