Exercising very slow for now

I was so glad to see other people need to start out execrising SLOWLY. I have had 3 joint replacements (had my right knee done in August 2011) and am trying to get into the habit of exercising. I am cleared by PT and physician to exercise. Just approaching a treadmill is an accomplishment! My question is how can I record on MFP my treadmill exercise when the slowest they go is 2.0 mph. I tried that and didn't last even 1 minute! Right now I start out at 0.8 and gradually over 20 minutes can get up to 1.2 mph. I know it doesn't sound like alot of effort, but when you are morbidly obese, ANY EXERCISE is a plus and you build up your stamina at a slower pace then most people. Does anyone know or can MFP add an even slower walking pace than 2.0 mph; like 1.0?