Texas: can use deadly force to stop a robbery in progress, criminal trespassing (i.e. your front or back yard), property being stolen from your neighbor. However, it is not protected by the castle law, therefore while you are most likely not a subject for criminal legal action, you may still be sued in a civil court. Oklahoma - cannot do any of he above.
The stopping of a robbery is my understanding too. That in Oklahoma you can only defend yourself or family members. There are some members in here that think otherwise. I have yet to see where it's stated that you can defend another individual.