License Implementation

[Remco]

Hello,

I'm creating some dot.net pages and an dll.
The pages should be used within an existing dot.net web application using
the dll for licensing.

There are some interested customers who want to buy a license but I don't
want them to be able to use the pages and dll in more then the the agreed
website.

What is the best way to verify that a function call is coming from the
agreed website?

Do you have advise or some url's about this issue?

Thanks in advance,

Remco