IThen hit them with a fingertip strike to the throat while stepping in. As they are responding to this, you can drop your arm and hit them in the nuts.
Not sure whether I get you right.
But I think you describe what we teach as the most basic form of ude kime nage:
atemi to throat or face with the arm which delivers the kime to ukes arm. Stretching uke. Then atemi to the genitalia with the same hand. Dropping uke.