being was formerly used where we now use having. Being to go to a ball in a few days. .
in modern usage, is, are, was or were being, with a past participle following (as built, made, etc) indicates the process toward the completed result expressed by the participle. The form is or was building, in this passive signification, is idiomatic, and, if free from ambiguity, is commonly preferable to the modern is or was being built. The last form of speech is, however, sufficiently authorised by approved writers. The older expression was is, or was, a-building or in building. A man who is being strangled. (Lamb) While the article on burns was being written. (Froude) Fresh experience is always being gained. (Jowett (Thucyd))