Hello Tom, Thank you for your inquiry! The Uwatec by ScubaPro Aladin 2G Air / Nitrox Dive Computer Watch dive computer can only be programmed for 1 gas mixture at a time and it CANNOT be changed “on the fly”, meaning you cannot change the program while underwater. http://www.scuba.com/scuba-gear-17/009345/ScubaPro-Aladin-2G-Air---Nitrox-Dive-Computer-Watch.html
Please note: No dive computer can be changed while under water. If you have any questions or wish to place an order, please call us at 1-800-247-2822.