Hello, I have very solution for this purpose. It takes hard disk serial number to restrict the usage and have many stages of security mechanism implemented in different places. I have been into doing this stuff from last 4-5 years and have developed few custom mechanism as well just to project the DLL itself along with EX4 file. I am not sure about the kind of Expert that you will protect, but I have some other very good solution to enhance the professional look and usability of an Expert to another level. I am just quoting the price for security mechanism implementation and by default you will get some product enhancement and it comes with a free installer too. So its very easy to install into client's computer. It one touch installer and installs everything by single click. Its a product key based authorization, so every users will need to have one product key to register their computer. Multiple computers can be allowed on per key basis. So KEY A can have 5 computer and key B can have only one. Usage will be restricted to those computers only and as per your requirement it can be adjusted to account number as well as broker name also. This initial space would not be sufficient to detail everything here and I feel I could satisfy your requirement regarding this job nicely. Thank you very much and looking forward to hear from you soon. Best Regards... Roy