The only solution I can see is to look back at your previous best loads for around 5 reps for each exercise then use an online rep max calculator (http://www.bodybuilding.com/fun/other7.htm or http://www.allthingsgym.com/rep-max-calculator/) to obtain a projected 1rm then you will have to assume that your 15 rep max is approximately 65% of your projected 1rm, 10 rep max is approximately 75% of your projected 1rm and your 5 rep max is approximately 85% of your projected 1rm and then work back from those figures.