about to do

*about to do something

in the process of doing something. (*Typically: be ~; get ~.) I'd better be about my yard work.
See also: to
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
See also:
References in classic literature ?
Again, there is a third case,-- when some one is about to do an irreparable deed through ignorance, and makes the discovery before it is done.
No matter how prestigious her medical school, we are more interested in how many times our physician has successfully performed the exact procedure we are about to undergo than whether she got an A in biochemistry." Getting that A may be helpful for what she's about to do, but insufficient.
Fixed-hour prayer means that you are doing the same thing your fellow Christians have just done or are about to do or are doing in your time zone.
He said, "Come back to the Board because we're about to do two or three films and we need you."