We collect registration / entry fees. Most people pay with their credit card. If we wanted to give out codes so that less fortunate people could enter using this system how would we do that? For example could I give out 10 different codes with a value of $35 each and each time someone registered they would use one of the codes and then that code is rendered useless to anyone else.  OR ( preferred) can I give one $350 card/ coupon and each time a teacher registers a student the balance goes down until we get to zero?  While all fees are divisible by $35 some will be $70 and others $105 so I am concerned as to how to make sure you could do 105 and 70 with 35 "coupons" So if your cart was $105 how could you do three times $35- this is why I am thinking best to have a declining balance card value of $350 and when they use 105 it changes value to $245 then if you use $70 it changes value to 175 and so on.