Add Current Balance as a Selectable Email Variable

As the semester progresses, I start including a student's remaining balance in emails. Since I can't select this as a variable, I have to send each message individually and fill in the balance amount. It would be nice to be able to insert a student's current balance as a variable in emails. The "Pay Now" amount would be helpful as well since before Aid is disbursed, this is a more accurate indication of what they owe.