Along with registering your package(s) of custom functions with the Function Call Manager, the registerFunctionCall method is also used to specify a version number for each function that you create. In the previous example, the ConvertDate function is registered with the version number 0x01000300.
Assigning a version number to each function allows you to provide upgrades to single functions in extensions you have already distributed to users.
For example, if you distributed an extension containing a package of 50 functions for your application and then wanted to change the behavior of one of the functions, you could:
When the API initializes all of the extensions it would find two functions with the same package name and function name. It would deregister the one with the earlier version number thereby updating your application.