It is possible to injaculate. You might want to read The Multiple
Orgasmic Man. In this book you learn where to press so the sperm gets
back in the system instead of getting out. A second approach is
through Tantra. First, get your perineum muscles strong. Second, learn
to breathe. As the moment of orgasm gets closer and closer we tense up
rather than breathing and expanding the moment. It is called to Ride
the Waves. It is worth hitting the bookstore and also attending some
workshops. It is quite interesting to have sex in a meditative state
so we let go of a goal, we communicate to our partner where we are and
we shoot for transcendence. Once we get all the sex we want then we
just realize there is more and more. The process of spirituality
through the body, pleasure, communion and revolving the sexual energy.
My wife and i attended our first seminar in Esalen (Big Sur,
California) and books. It's been a beautiful journey and looking back
we thought how could we have missed such a pleasurable education.
Thanks for your question.