Yes there is. I can't tell you much about RR plug ins, but there is a way to do it. It is possible to do things like have the antenna go up when you press one button on the PC and go down when you press another. There are multiple ways to achieve this, but the one that sticks out in my mind is through inputs in the PC's parallel or serial port.
It's important to keep in mind the concept of the antenna. You might already know about it, but I'll mention it anyways to provide the foundation of how it will interface with the computer. A power antenna has a motor that has two wires, positive and negative. You connect the wires to a 12 volt source and it will spin. Reverse the connections and it will spin the opposite direction.
Now we get to the computer. Connect the wires to a relay. The relay will get a signal from the pins on the parallel or serial port on your computer. The relay will then apply voltage to the antenna motor, thereby spinning it. The pins on the computer's serial or parallel port will send voltage to the relay from a program on the computer, or through the registry after you hack it. The program tell the serial or parallel pins to send a signal (voltage) to the relay based on actions you perform. This might be pressing a button on a touch screen, which is essentially a mouse click. The button could be one designed for bringing out the antenna or lowering it.
This is a somewhat simplified explanation of the concept behind the interaction of computers and car accessories through serial and parallel ports, but it's not by any means a comprehensive one. I suggest you search for other threads involving using serial and parallel pins to control car accessories. This will at least point you in the right direction.