VBA registry interface

To answer your first question, yes, it would be possible, but it's going to be a hassle. You'll need to create a separate "installer" program which installs the worksheet and registers the installation date in the system registry. Every time your worksheet is opened, it can check the registry and, if the current date is more than 14 days after the installation date, deny access to the functions.

As far as making sure the spreadsheet isn't redistributed, there really isn't a good way to do this. The best approach, I believe, would be a remote registration process such as Windows XP activation uses. Think hard about whether you really want to do this -- I think this is considerably more work than you've bargained for.

On another note, I'm not sure Microsoft would approve of your distributing VBA modules (embedded in Excel worksheets) on a commercial basis. I could be wrong about that, but it might not be a bad idea to check it out.

duckthing at 2007-8-30 >

Hi,

I'm going to disagree with duckthing about using the registry. It's fairly easy to add keys to registry without needing to write an installer. You can use the windows api HOWEVER you need to be sure you know what your doing. You'd could use the windows api to read the key. You'd have to encrypt the key value so that it's not that easy to change though.

I'm also going to disagree about preventing it from being redistributable (sorry duckthing) but it requires the user to have a network card or modem. Each machine in the world has a unique MAC address, prior to giving the user a copy of your spreadsheet you'd need to ask your user to supply their MAC address, you would need to embed that into your code, i.e. if machines MAC address = "something" then run.

You'll need to use the windows api again... heres a wonderful example of how to do that

http://www.osix.net/modules/article/print.php?id=2

DerekSmyth at 2007-8-30 >

Derek Smyth wrote:

I'm going to disagree with duckthing about using the registry. It's fairly easy to add keys to registry without needing to write an installer. You can use the windows api HOWEVER you need to be sure you know what your doing. You'd could use the windows api to read the key. You'd have to encrypt the key value so that it's not that easy to change though.

Yes, you're absolutely right. I wasn't thinking clearly! What the workbook could do, then, is to first check to see if the appropriate key exists. If it doesn't, the workbook can assume this is the first time it's being run, and set up the necessary key. And, of course, he'd need to make sure his code is locked for viewing.

Depending on the user's security policies, the program may not be allowed to write to the registry. But it's a starting point.

(Just to clarify, I wasn't implying that he needs to create some massive InstallShield installation process. )

duckthing at 2007-8-30 >

Derek Smyth wrote:

It's kind of tricky protecting software, where there is a will there is a way. Protecting spreadsheets is even more tricky.

If it were easy, every software company on the planet would already be doing it! I think Microsoft's product activation process is the closest I've seen to a secure, reliable process for verifying software installations -- but it's not a model most "hobbyist" or "freelance" developers can implement.

Cheers!

duckthing at 2007-8-30 >