Adding another infix operator?(programing)

Hello, I am new to ginac. I have a computer algebra program which uses the infix operator "**" for a noncommutative multiplication (for example, a**b where a and b are symbols, but are thought of as representing matrices). (See http://math.ucsd.edu/~ncalg for more.) Is it possible/easy/hard to add a "**" infix operator to ginac? If so, where do I start looking in the code to do this. I would like to link my code up with ginac in the future. Mark Stankus mstankus@calpoly.edu