I dont know how far through your trainnig you are, but have you been introduced to a "whizzwheel" flight computer? If you have work out your Groundspeed using the wind side then put this speed at the top of the wheel then look at the time you want, say 22 mins then read of how far you have gone.
If you havent well, Distance = Speed x Time, the only problem will be working out your groundspeed, i would wait till you are taught to use the computer.