One thing to understand about the word Kamma in Pali, or Karma in Sanskrit, is that it means actions. Or even our speech, our thoughts as well. It means something that we have done. It is not the result of a past thing, it is something we are doing. A lot of people get that confused. "The Kamma that you are experiencing now," that's not really the right expression. You are experiencing the results of past Kamma. So there is a slight change on the word. It is used in different ways, but as far as Theravadin Buddhism goes, Kamma is really what you are doing. Everything you have done in the past is your Kamma. The results are what you experience. Your reaction is then your new Kamma. Not what is coming, your reaction is then your new Kamma.
So re-expressing this question, "Can the Kamma being experienced in this life be the result of actions in this life?" OK, "Kamma that you experience now." Not Kamma, but the results of Kamma you experience right now, can be the result of something you did in this life. And Buddhism says it can be the result of something you did in a past life.
One of the most bizarre Kammic type people on the planet right now is Christopher Reeve. He is the American actor who became paralyzed from the neck down. He was very wealthy, he was very popular, he was Superman in the movies, famous, lots of friends etc. Then, all of a sudden, he fell off a horse and was paralyzed from the neck down. From what I know, he really didn't deserve that as a result of things he did in this life. He wasn't an evil person so to speak. Buddhism would say that him falling off the horse and becoming paralyzed was a result of past lives. Now what he is doing, making new Kamma, is super good. He is working on helping people get over these debilitating injuries, he is raising more money in the United States Congress, he is doing lots of things. He is also proving the predictions wrong about what should happen to someone in his condition after five or six years.
He is actually developing movement in a wrist, I think, also in his feet, and he has sensation throughout his whole skin now. He didn't have that when he was injured. Supposedly no-one is supposed to improve after the first six months, and he is still improving after five or six years. So, what he is doing now is new, in response to what he experienced. So, OK, he had some bad Kamma way back. He did something wrong, Buddhism would say, but seemingly in a past life. He got the result, but you know since he was already rich and wealthy, he was experiencing the result of good stuff by being rich and wealthy. He gets this very bad Kamma, he almost wants to die and his wife talks him into living. He stays, and he changes his whole mind state about what he is doing with his life, and all of a sudden, lots of good Kamma is coming at him.
This, in a sense, when you think of Kamma and the results of Kamma, is bizarre. And somewhere in the scriptures, I think a couple of times, if not more, the Buddha is being asked a lot of questions about Kamma. He basically says to people similar words to: If you try to understand everything about Kamma with your intellect, you will go insane. It is that bizarre, we can't really see it that well. Basically according to the teaching, whatever you experience is the result of past Kamma, but it is in that experience, in your reaction, that you make new Kamma.