checking registry entry on Auto_open in excel addin

Hi friends,
I have an add-in which I want to protect from piracy.

Can I somehow write a code in Auto_Open that will access the registry entry and will verify if the installation is genuine..

I have an installer that on installation adds few details in the registry and also installs the add-in on clients machine. I just need a code to be used in 'add-in' so that it cannot be distributed illegally..

I hope I am able to explain my problem.. If there is anything more you need about it please let me know..

Regards,
Vaibhav

Thanks for the reply..

Basically the customers that I am targetting are not much into computers.. they would not put efforts to do anything to hack the add-in..

However they might distribute it through email and that is the only thing that i need to protect..

Also i'll see the help file for 'Save Setting' & 'GetSetting'.. If I dont understand anything i'll get back to you..

Besides Registry entries is there any other easier way to protect the add-in to run only on specifed computers. Even if it is not 100% foolproof will do..

Thanks & Regards,
Vaibhav