Garmin Panel mounted to handleld interface (155xl-696)

Hello, I have my 155XL connected to my 696 unit via RS232 out on the 155 and in on the 696 which makes the 696 basically a color screen slave making the 155XL really usable as it displays all the functions of the panel unit on the big color screen. I was wondering what would happen if I connect the RS232 OUT on the 696 and feed data back into the 155XL, would I be able to control function on the 155xl through the 696? wondering if anyone has any experience in this