auto-updating DLL / updateable BHO

Overview – The company created an IE BHO. Goal - Alter the BHO to call a php page for newer version, and if there is one, update itself. Working in our BHO framework or creating a BHO that does this - that we can port the code from - either is fine. Source code should be in C# in a Visual Studio 2010 project. Assumed: The DLL should not be flagged by anti virus application and must not operate in anyway which might be considered harmful or dangerous to a PC. We have the means to sign the dll.