You'd need access to the Windows OpenGL ICD DDK which is one of the few things Microsoft doesn't hand out freely and without signing a NDA (unless the situation somehow changed withing the past few years).

OTOH the ICD API should be easy enough to reverse engineer. The registry keys, where the OpenGL ICD is registered are well known and there are plenty of drivers in plenty of versions you can dissect to learn how to talk "ICD".