bmi graph needed

I need a graph that when a person inputs certain information it will automatically respond to them with their Body Mass Index(BMI) number. this number determines their state of wellness based on their weight and age. It will send the user a response and also send me their information such as ...name, age, height, bmi number, email and telephone number if they wish to receive a call from a consultant. I t will have to be uploaded to my site on all pages and highlighted or flashed to induce use. I may be leaving something out at the moment but will modify if need be.