Protecting/Licensing a dll???

Hi fellas,

I have created a dll which happens to the core of my application.

But, the problem is any one having this dll can use it!!! :(

Thus, I would like to create a sort of license for it (the way we have in ocx components)

I am not sure how to implement it!!! :confused:

Can any one show how???

Thanks,
Subhendu
:) :) :)