you could use an array, stack, or queu, but... remember that when you close your form it resets all your variables. honestly, the only way i could see doing it, without using a table, would to make it write to a txt file and load the txtfile everytime you opened the form. You could also then clear the txtfile each day with a button, or manually select and delete.
Honestly, I would use another table, indexed by date - this way you still have a record of who was trained on what day.
still your options are open Cruz'n and Booz'n always.
This post shows what little I do at work.