Anti Piracy Registration Check

I am selling a Dll written in VC++ v6. The problem is that I want to be able to provide a demo/trial copy of the dll for potential customers to use before deciding on making a purchase. All of my previous attempts at adding some sort of functionality that will cause the trial copy to expire after a certain time or number of uses have been worked around and patches released for it. I would like someone to think of a way of adding some sort of expirey to the Dll whilst still letting a potential customer fairly evaluate the product. I do not want to release a trial Dll with missing features as that results in lost sales as well. What I am more requiring is an idea here as to how people think that this may be done. I will also be wanting someone to write this code for me (in VC++ v6, such that I can integrate it with my Dll). If you could please include your idea along with your bid, I will select a bid that has the best idea, not the lowest price. The trouble with a Dll is that it may be trialed under ASP which will mean that code running in the Dll may have no access to the registry or any directory except windows\temp I would also like this to work under the .NET platform. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Complete ownership and distribution copyrights to all work purchased. ## Platform Windows (All versions) must be able to work on .NET platform as well