track and graph users time spent exercising

I am looking for a plugin that will allow users to enter the time they spend exercising and then graph the results for the week and cumulatively. My use is for my daughter’s soccer team, where the girls are supposed to track the minutes they spend doing the “homework” drills each day. The hope is having it graphed on the blog would motivate them to train regularly. (positive peer pressure). I have not been able to find a plugin that seems to do this. Anyone know of a plugin that would work?