Restricting End user

[Anon]

I recently wrote a meta search script, which searches 3 search engines and output the results through template files. I am planning to add 'Add to Mybookmars', 'Search only this site' and couple of more features to it. I am planning to sell this script. Now i've got one problem. Actually i want to have a feature where the end user, who purchases my script, cannot use the script on any other domain other than his own. I am talking about something like the feature are with windows based application i.e Enter registration code
If somebody has any idea as to how it can be down than please help me.

Any help would be truly appreciated.

Cheers
San

[junebug]

well, add a few lines into the script that require a certain registration number to be found for it to work. if the number is not found, have the script print out a denail message. be creative about it because if the script is readable, digging into it to find the lines asking for this won't take too long.

[Anon]

Chris,
Thanks for the reply.
I am too interested for this kinda things. As i m not at all that good in programming i cannot really make this happen. If you can print certain codes here, it would be really good.
Cheers
San