As an aside, how do you get to the bytecodeyou use? Do you write quazi-assembly by hand? Did you develop your own compiler? For what language?
Will other, non-microsoft assistive technologies, like NVDA for example, be able to use it?
As for how the bytecode is built, the GitHub repository I linked has a library with a WinRT API for building the bytecode at run time, by calling methods that correspond to the individual opcodes. It's an object-oriented API, so there's a class for each type of operand. And for control flow blocks (e.g. if-else and while loops), the method takes a WinRT delegate (basically a lambda) that builds the body of the block. You can see how it works in the functional tests; stay tuned for actual sample code.