not too clear but i think you want
CSG so you can "make holes" anywhere in a given object? unfortunately, Jack's
previous mention of it found crickets (not sure if they were offering to add it or simply bringing up the topic) but it CSG would open doors (or windows. pick a pun
).
otherwise, you could code a simple "insert window into wall" function using (multiple) primatives or pre-built "building block" models.
in reality, it depends on what level of functionality you're looking for so if you wouldn't mind elaborating?