Expert Advisor DLL protection

I need somebody who can (who has previous experience in this type of development and integration with mq4)protect my Expert Advisor mq4 file! The contents of the file are 3 or 4 functions with simple mathematical operations [login to view URL] the most parts of the mq4 Code into Dll and protect it! I don`t know which protection is the best! You have any ideas which is the best and safest method? VERY IMPORTANT: Make that way,that this DLL file would not work on another PC.I see that like,I give person a genarator ,he makes a key (attached to his motherboard,hard drive,smth like that etc..) I am making him a DLL (where will be a part of mq4 file ) and giving him it away,so the software should work only with DLL file + mq4 file,most parts are [login to view URL] like that . So I want that only the buyer can use this tool and can't see the code. I have found smth like I want AN EXAMPLE : [login to view URL] Also appreciate suggestions to improve the protection.