If you allow your clients to open your workbooks, they are more or less
defenseless (I've seen some pretty good layered defenses, but they all
fell to attacks that are publicly available, or commercially available
at low cost). If you build everything into a COM add-in, you have the
best (and pretty good) security you can get with XL. But short of that,
you may do better to sell them with minimal or no protection, and
develop a great relationship with your clients.

In article ,
Bill R wrote:

I know passwords can be easily broken so what can I do to really protect
them. Is there a good program out that will totally protect the password in
my workbooks? I want to sell my workbooks without fear of them being disected.

Thanks.